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All About Circuits Forum - Blogs http://forum.allaboutcircuits.com/blog.php A discussion forum for electronics and circuits en Sat, 21 Nov 2009 06:01:33 GMT vBulletin 60 http://forum.allaboutcircuits.com/images/misc/rss.jpg All About Circuits Forum - Blogs http://forum.allaboutcircuits.com/blog.php Deesigns are (almost) finished http://forum.allaboutcircuits.com/blog.php?b=385 Wed, 11 Nov 2009 06:51:39 GMT Ok the computer is really starting to take shape. So, the schematics for the ALU ARE DONE!!! and will upload them in a pdf. The accumulator is also... Ok the computer is really starting to take shape. So, the schematics for the ALU ARE DONE!!! and will upload them in a pdf. The accumulator is also done but the main processor...well....lets just say i needs to be checked first.

If someone could check it for me the just send me a message by this forum or :

kiwisoftware@hotmail.co.uk

the code is as follows:

0000 - add (adds two numbers and stores in accumulator)
0001 - adm (adds number in accumulator with word B)
0010 - sub (subtracts two numbers and stores in accumulator)
0011 - sbm (subtracts number in accumulator with word B)
0100 - AND (AND operation with word A and B, then stores in accumulator)
0101 - ANM (AND operation with accumulator and word B, then stores in accumulator)
0110 - OR* (OR operation with word A and B, then stores in accumulator)
0111 - ORM (OR operation with accumulator and word B, then stores in accumulator)
1000 - NOT (NOT operation with word A then stores in accumulator)
1001 - NOM (NOT operation with accumulator, then stores in accumulator)
1010 - EXO (EXOR operation with word A and B, then stores in accumulator)
1011 - EXM (EXOR operation with accumulator and word B, then stores in accumulator)
1100 - COM (Compare Accumulator word with word B)
1101 - SAV (Saves words A, B and instruction into memory)
1110 - LOD (Loads words A, B and instruction)
1111 - RES (Resets everything)

notice that the COM compares accumulator word and word B because if i just compared word A and B then if i was to make a program i could never compare a result with anything :( but know i have fixed it :)

thanks for reading and GIVE ME ALL YOUR KNOWLEDGE!!! ]]> MITCH electronics http://forum.allaboutcircuits.com/blog.php?b=385 ALU getting there http://forum.allaboutcircuits.com/blog.php?b=384 Sat, 31 Oct 2009 16:49:43 GMT I have completly redesigned the ALU after discovering i need decoupling capacators and open collectors. I am using the Eagle software to draw the... I have completly redesigned the ALU after discovering i need decoupling capacators and open collectors. I am using the Eagle software to draw the schematics and convert to PCB, man....I have never used such a brilliant program for auto-routing. This thing can route ANYTHING!!! ]]> MITCH electronics http://forum.allaboutcircuits.com/blog.php?b=384 4-Bit Computer Project http://forum.allaboutcircuits.com/blog.php?b=383 Wed, 28 Oct 2009 14:00:44 GMT Well I have finished the ALU design and just need to implement this to a PCB. Instead of the traditional "everything on one board" I have designed mini boards that fit in a mini shelf (i mean really small). This way its easier to find a problem and fix. ]]> MITCH electronics http://forum.allaboutcircuits.com/blog.php?b=383 Quick exercise in, design of a , Volt.PK. Detector http://forum.allaboutcircuits.com/blog.php?b=382 Wed, 07 Oct 2009 00:32:28 GMT Design: Voltage Peak detector 1. Vcc = 12v. 2. Choose VCQ1 output, = 9v. 3. Choose VBQ1 = 8v. 4. VEQ1 = 7.3v. Design:
Voltage Peak detector

1. Vcc = 12v.

2. Choose VCQ1 output, = 9v.

3. Choose VBQ1 = 8v.

4. VEQ1 = 7.3v.

5. choose RCQ1 = 470 ohms. (to drive a LED output)

6. IRCQ1 = (Vcc - VCQ1) / RCQ1 = ~ 6.38 mA.

7. RE is a split resistance, between the emitter of Q1 and Q2.
RE = ( REQ1 + REQ2) = (VEQ1 / IRCQ1) = ~ 1143 ohms.
So make REQ1 = REQ2 = 560 ohms each.

8. Now VEQ2 = ~ 3.65v.

9. Now with around 1100 ohms for RE, then make RB1Q1 around 2 times RE =~ 2K ohms.

10 IRB1Q1 = (VBQ1 / RB1Q1) = 4mA.

11. RB2Q1 = (Vcc - VBQ1) / IRB1Q1 = 1K ohms.

By varying the resistor value of REQ2, to a higher value, will increase VEQ2, which in turn will then detect a higher PK input voltage.

This will also raise the idle (standing voltage) at the output too.

Idle output voltage.
Input @ 4v.
No trigger of circuit.

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Input voltagte @ 4.3V.
The circuit is triggered.

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]]> hobbyist http://forum.allaboutcircuits.com/blog.php?b=382 CookBook Entries http://forum.allaboutcircuits.com/blog.php?b=381 Sat, 03 Oct 2009 20:41:19 GMT This section will encompase basic circuits people might use. If a schematic is found to be flawed, it will be repaired or removed. This section will encompase basic circuits people might use. If a schematic is found to be flawed, it will be repaired or removed. ]]> Bill_Marsden http://forum.allaboutcircuits.com/blog.php?b=381 LEDs, 555s, PWM, Flashers, and Light Chasers Index http://forum.allaboutcircuits.com/blog.php?b=378 Sun, 20 Sep 2009 03:39:41 GMT LEDs, 555s, PWM, Flashers, and Light Chasers

I'm moving this article to blog format to allow me greater flexability in editing. Please, do not comment in the blog, if you do I will delete it. If you want to leave a comment do it here.

One of the most common requests at All About Circuits is various methods of flashing LEDs. I'll try to show most of the techniques used for this purpose that have been covered on this site, explaining how and why along the way.

Index

1....LEDs
2....Current Limiting
3....The LED / Resistor Only Bargraph
4....The 555 Integrated Circuit
5....The 555 and PWM
6....Low Power Applications
7....The Joule Thief
8....From Four, Twenty
9....Light Chasers
10.l.Transistor Drivers
11.l.Making Patterns
l.....Conclusion

]]> Bill_Marsden http://forum.allaboutcircuits.com/blog.php?b=378 small sig.amp completed. http://forum.allaboutcircuits.com/blog.php?b=377 Sun, 19 Jul 2009 21:35:49 GMT Page 3. If this works properly I will post this particular design page in the electronics general category for people to look at and suggest design... Page 3.
If this works properly I will post this particular design page in the electronics general category
for people to look at and suggest design corrections, for beginners to learn from.

This can be scrutinized by people more knowledgeable to give good design suggestions so everyone starting
out in this field can benefit from the learning in this thread.
　
VCC = 12V.
Freq. = 400 Hz.
Vin pk. = 10mV.
VinZout = 700 ohms.
Vout pk. = 4V.
Rload = 200 ohms.
-----------------------
I will approach this design by designing CC amp. for the output to drive the load.

Stage Q1:
Vin pk. = 4V.
Re1 = 200 ohms to match Rload.
C1 = 100uF

These next steps are done experimentally because of the low VCC with respect to Vin.
Now since Vin is very high with respect to the VCC I will make RB1 around 100 > RE1

RB1 = 22K
Now hooking my generator to the input of this CC. amp. and scoping the input and output,
I use my res.sub.box. to test resistors between base and VCC, until I get a proper waveform
close to 4V pk. across a 200 ohm load. (that value is RB2)

RB2 = 3.9K

Dynamic test:
A good waveform across Rload, the amp can only take around 4V. input before it distorts
so because of the low VCC with respect to the output swing needed, the output across the Rload
is a little more than 3.8V pk. close to design values, shoiuld I realy need a 4V. out, than
I would have to use different transistors (fet, power trans, ect..). But this is just a experimental
design.
To see how stable the stage was, due to base current loading on the divider, I did the 5 transistor
substitute on this stage and the Vb, VE, and waveform amplitude and structure remained close to same,
values throughout. No significant change in the output wave.

It passed the base current loading affect test, so this stage is somewhat stable in variations of IB.

Calculate Zin estimated around 1.2K - 2.4K using Beta from (20 - 100)
Now I have a output voltage across the Load as reqired.

The Zin is still too low for me to multistage CE amps into it yet.

So I will keep the scope at the output of this stage and design another CC. amp to cap. feed into it
using a RE2 value of 1K.

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---------------------------
　
Stage Q2:
RE2 = 1K
RB3 = 33K
RB4 = 22K

Dynamic test:

Well when I hooked up the input signal I had to lower it's amplitude now the output signal has excellent
waveshape and the amplitude is right at 4V. pk. Even when I disconnect and connect the 200 ohm LOAD
there is hardly any noticeable change in both the amplitude and shape of waveform. Very good.

Zin is now around (6k - 10k) OHMS.
I think I have enough impedance to develope a 4V. pk signal across with a CE amp stage.

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-------------------------------
Stage Q3:

RC3 = 4.7K
VCQ3 = 6V.
ICQ3 = 1.27mA.
Av. = 20 no load
RE3 = 220
VRE3 = 279mV.
VRB5 = 0.98V.
RB5 = 8.2K
IRB5 = 119uA.
RB6 = 91K

static test:

VC = 5.7V.
VRB5 = 1V.

dynamic test:

Waveform shows good amplitude close to 4.5V. pk. input signal needed lowered, for that stage.
Now OVERALL performance to this point, scoping Vout. at the RLOAD and scoping Vin aqt stage Q3,
shows excellent waveform and amplitude rides comfortably at a peek of 4V. across the 200 ohm load.

Disconnecting the load gives No real significant change in the Vout, of amp, and Vin is at 300mV.

I changed the transistors in all 3 stages 3 times and got the ame output waveform.
Good amplifying so far.

So 3 stages Av. is around (4V / 300mV) = 13.3
Zin = (2.7K - 5.6K) Beta (20 -100)

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------------------------
Stage Q4:

RC4 = 2K
VCQ4 = 6V
ICQ4 = 3mA.
Av. = 20 no load
RE4 = 100
VRE4 = 300mV.
VRB7 = 1V.
RB7 = 6.8K
IRB7 = 147uA
RB8 = 75K
static test:
VC = 7V
VRB7 = 0.97V

Dynamic test:
Good signal waveform and amplitude:
COMPLETED AND WORKS GOOD.
----------------------------------------------
OVERALL PERFORMANCE
Vin = 8mV
Vout = 4V
RLOAD = 200 ohms.
When I connect or disconnect the LOAD there is NO apparent change in Vout amplitude nor waveform shape.
Av. = 500

When I got to the last stage and connected it to the rest of the amp, I got a lot of rf noise on the scope
I put in a 0.1 uf cap from the base of Q3 to ground to filter the noise and got a nice strong waveform,
however I was getting 4 Volt. out with 20mV. input, so I placed the AC bypass across emitter res.RE3 to bring
a nice 4V. output with a 8mV. input. So I was able to recover the gain needed to put 4.Vout @ 10.mVin.

No feedback capacitors were used, therefore a very slight phase shift from input to output.

Changed every transistor with different ones, couple times and get the same output waveform.

I designed it with my generator set at 400Hz.
So this amp is more like a narrow bandpass amplifier it only amplifies at peek voltage from 400 to around 900 Hz.
It amplifies about a 500 HZ bandwith very narrow.

This is a experiment in trying to design using a logical approach of attempting to amplify a small signal
from a impedance mismatch between input and output from a high impedance 700 ohms to a low 200 ohms output.

With a Vcc that is just large enough to handle the signal voltage of 4V. peek.

Also using NPN 2n3904 transistors throughout the design.
　
Vout at the RLOAD is 4V. pk.

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]]> hobbyist http://forum.allaboutcircuits.com/blog.php?b=377 small signal amp exp. page 3 http://forum.allaboutcircuits.com/blog.php?b=376 Fri, 17 Jul 2009 14:43:20 GMT PAGE 3 REDESIGN working from input to output stage.

At this point I'm running into clipping problems when I add a fourth stage,
I check the DC bias for each stage and the VC. is around the 1/2 VCC area.

I check the Av. each individually, and I get the gains required, but coupling them is when I run into problems,
with clipping of the waveform.

So I will start over again:

This time I need to check the audio frequency generator, Volt output, because when I get in the very low millivolt region
I run into problems with signal oscilating and rf noise. Showing on my scope.

Audio generator = 10mV. pk. @ Zout = 700 ohms is the minimum where there is good clarity of the waveform on the scope.

So I will use that as my baseline Vin. for my amp design.

Now since my Vin, is established I will design from the input to the output stage, that way I can design each stage Zin,
with the proper Vb, needed to handle the signal each stage recieves, because I think what was happening was that the signal
was overdriving the stages. so I will use the input voltage to determine as much as possible, what value of Vb I need for each stage.

Vin. pk. = 10mV.
Vout. pk. = 4V.
Rload = 200 ohms.
VCC = 12V.

Alright Now I'm getting somewhere with this,
I hace been running into problems with overdriving the stages, and impedances, so when I took all coupling caps out and disconnected the load on the output stage, so now my transisitor stage is just DC analysis only, I measured my VC, and VB, everything looked good, then keeping my voltmeter hooked to VB point, (2.36V)

I coupled the signal generator into this stage, and observed the waveform with negative peaks around 4 volts, but positive flats at around 3 volts. Then I observed on the voltmeter, that VB was reading
- 0.47V, so as I decreased signal input the voltage began to rise to 0V.
and then eventualy back to 2.36V. and the waveform was around 1V pk.
with zero distortion.

I calculated the voltage pk. on my scope to be 700mV pk.
I've read it in all my course books about the input signal driving a transistor stage into saturation, and things, but now I understand this much better, that the signal should have NO affect on the BIAS of the stage it's feeding into, which means signal impedance must be lower than stage impedance, as well as base voltage must be sufficiently higher than pk. voltage of input signal to handle the excursion in a linear way.

My method now will be to design the stages from the input going to the output, trying to keep the voltage VB at each stage to be around 4 times greater than the signal feeding into it. And see if that helps keep the stages from overdriving eachother. ]]> hobbyist http://forum.allaboutcircuits.com/blog.php?b=376 small signal amp experiment cont. page 2 http://forum.allaboutcircuits.com/blog.php?b=375 Thu, 16 Jul 2009 23:12:45 GMT Ok Now I've been working on the next stage, and realizing that the Zin is dropping instead of increasing, as I try to get as much gain as possible.

Probably if I were to use bypass caps. It would solve most of this but I'm trying to not have to use bypass caps. if I don't have to.

My other alternative is to start over, and make the Volt. gain. of the output stages low and begin to increase the gains as I approach the input stages,

that way I can use larger values for the emitter resistors, which will increase the Zin so I can get out of this low value Zin hole, I dug myself into.

It's amazing when you really try to work within constraints, how there is a lot more work that has to go into getting the right values, so that transistor parameters, mainly base current loading don't affect the bias of the stage.

To be cont:
------------------------------------------------------------------------------------
PAGE 2. REDESIGN with lower Av. at the output.

arbitrary chosen = #

F = 400 HZ #
Vout pk = 4V. #
RLOAD = 200 ohms #
VCC = 12V. = (3 x Vout pk) #
-------------------------------------------------------
Stage Q1:

VC = 6V.
ICmax pk = 100 mA. #
Vout pk = 4V. #
VC- pk-pk = 2V.-10V.
ICmin = VC of 10V. so 2V. dropped across RC = VRCmin
ICmax = VC of 2V. so 10V is dropped across RC = VRCmax. @ ICmax of 100mA.
Rout = RC1 // RL = { ( VRCmax / ICmax.)} = { (10V. / 100mA.)} = 100 ohms.
RC1 = RL = (2 x Rout) = 200 ohms.
ICQ1 = ( VC / RC) = (6 / 200) = 30mA.
RC1 = 200
Av. 2 #
RE1 = (Rout / Av.) = 51 ohms
VRE1 = 1.53V.
VRB1 = 2.23V.
RB1 = 1K ohms #
IB1 = 2.23mA
RB2 = 4.3K ohms

static test:
When I build the volt. divider, I will test 5 different transistors for that stage and if the base current loading remains close to the same with all 5 then that divider will be used in the design of that stage.

VCQ1 = 6.54V.
VEQ1 = 1.5V.
VRB1 = 2.2V.

Dynamic test:
Vin pk. = 220mV. pk.
Vout pk. = 300mV pk.
Av = 1.36
Zin = 615 ohms using 50 for Beta. calculations
Not much to be said for that stage.
-----------------------------------------------------------------------------
Stage Q2:

RC2 = 620 ohms
Rout = 310 ohms approx.
VCQ2 = 6V.
ICQ2 = 9.67mA
Av. = 2 #
RE2 = 150
VRE2 = 1.45V.
RB3 = 3.3K #
VRB3 = 2.15V.
IRB3 = 652uA.
RB4 = 15K

static test:
VCQ2 = 6.72
VEQ2 =1.37
VRB3 =2.06

dynamic test: (Vout at the output stageQ1)

Vin pk Q2 = 360mV pk.
Vout pk Q1 = 1V. pk.
Av. 2.77
Zin = 1987 ohms (beta = 50)
Zin going up to 2K now. That's good..
-------------------------------------------------------------------------------------
Stage Q3: (It's time to go with a darlington pair.)

RC3 = 2K
Rout = 1K
VCQ3 = 6V.
ICQ3 = 3mA.
Av. 20 #
RE3 = 51 ohms (Rout / 20)
VRE3 = 153mV.
VRB5 = 1.353V.
(It seems like when calculating Vbe of a darlington pair need to use 1.2V for total Vbe of transistors together instead of nom.1.4V)

RB5 = 5.6K ohms #
IRB5 = 241uA.
RB6 = 44K ohms (43K + 1K) in series.

static test:
VCQ3 =6.2V.
VEQ3 =0.19V
VRB5 =1.39V.

Dynamic test:
Av. overall 50
Vin pk. = 20mV.
Vout pk. = 1V

Zin = 5K ohms (Where trans. betas x RE3 = into 100,000's so can be ignored in the calculations zin.)

To be cont: On page 3 ]]> hobbyist http://forum.allaboutcircuits.com/blog.php?b=375 Digital thermometer http://forum.allaboutcircuits.com/blog.php?b=374 Thu, 16 Jul 2009 15:21:04 GMT My first project with an ATMEL AVR microcontroller (ATMega8). I use the DS1820 digital temperature meter. ... My first project with an ATMEL AVR microcontroller (ATMega8). I use the DS1820 digital temperature meter.

http://www.youtube.com/watch?v=ToWDsdDHvas

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]]> mik3 http://forum.allaboutcircuits.com/blog.php?b=374 Small signal amp proper design experiment http://forum.allaboutcircuits.com/blog.php?b=373 Wed, 15 Jul 2009 03:12:35 GMT 　
As a hobbiest (NON engineer), I am designing a small signal amp in the most proper way I know how through my methods of calculations, and imperical breadboarding and measurements and tests, using a calculator breadboard and components, oscilloscope, audio signal generator,
resistor sub box. and multimeters. My method is design and build and test and make adjustments as necessary, and recalculate build and test until it works according to the constraints I put for it.
This will be added to as I progress in this project...
　
arbitrary chosen = #　

F = 400 HZ #
Vout pk = 4V. #
Av. = 4000 #
Vin pk. = 1mV. #
Zin > 10K #
VCC = 12V. = (3 x Vout pk) #
-------------------------------------------------------
Stage Q1:
VC = 6V.
ICmax pk = 100 mA. #
Vout pk = 4V. #
VC- pk-pk = 2V.-10V.
ICmin = VC of 10V. so 2V. dropped across RC = VRCmin
ICmax = VC of 2V. so 10V is dropped across RC = VRCmax. @ ICmax of 100mA.
Rout = RC1 // RL = { ( VRCmax / ICmax.)} = { (10V. / 100mA.)} = 100 ohms.
RC1 = RL = (2 x Rout) = 200 ohms.
ICQ1 = ( VC / RC) = (6 / 200) = 30mA.
RC1 = 200
Av. 10 #
RE1 = (Rout / Av.) = 10
VRE1 = 0.3V
VRB1 = 1V
RB1 = 180 #
IB1 = 5.5mA
RB2 = 1.8K
Vinsig. = ( Vout pk. / Av. ) = (4 / 10) = 0.4Vin pk.
　
static measure:
VC1 = 5.7V.
VB1 = 1.07V.

Dynamic test:
NO load = Vinsig pk. 400mV (distortion on the positive pk.) flat @ 350mV.pos. pk.
NO load = Vinsig pk. 200mV. (NO distortion)

Conclusion : No load causes a change in the INPUT waveform:
Lower Vinsig. removes distortion, normal waveform.
Raise Vinsig. to designed value 400mV. with No load and check VRE1,
VRE1 = 0.33V. NO load
VRE1 = 0.35V. 200 ohm load.
IRE1 = 33mA - 35mA.
delta IRE1 = 2mA.
Shows that With the small value of RE1 of 10 ohms causes more IB to flow under heavy
Vsigin, thereby shunting the signal. When I replace the 200 ohm load, then Vinsig. has proper waveform, no distortion, @400mV pk. but Vout pk, shows around 3.5V pk.
Res. sub box, shows 300 ohms Load, gives me design values of 400mV pk. Vin,
with Vout pk. of 4 volts NO distortion.
Assuming a low Beta, of 50, would make RE1 be around 500 ohms to the signal, so it is the divider resistors that needs to be raised to get a higher Zin.
So to get 4V. pk. out @ 200 ohm load which is my constraints I will rework the divider resistors, for a higher values.

to be continued:

This is very interesting, if I raise RB1 the waveform gets worst, but if I lower it from 180 to 164 ohms, then VC is at 6.03V. the input waveform is almost no distortion, but doesn't quite reach 400mV, pk on the pos half, but reaches it on the neg side.

YThis is going to be a project in learning how to design the input impedance of a basic amp, load value as well as all the other components contribute to the signal input waveform, as the transistor conducts less the signal input has less distortion, but the amplitude goes down, as the transistor conducts more beyond certain value the signal input goes down in amplitude while remaining NO distortion.

This is a whole new learning experiance in amp design, just getting the proper values needed to keep the integrity of the input signal.

To be continued:
　
Alright Now I'm getting somewhere,

First I disconnected the generator from the amp stage and set my generator with my oscilloscope to read 400mV pk.
Then hooked it up to the input of the amp stage and the waveform dropped to exactly 100mV. pk. (input signal)

Now I disconected the emitter resistor first and seen no big change in recovering the input amplitude, put back the emitter RE1 resistor, and disconnected the divider resistors, RB1 and RB2, and the signal amplitude was restored, with no distortion.

WHY THE DISTORTION?

Now for all the distortion I was getting before, was because of the stupidity, of raising the input voltage with the signal connected to the amp. That's a NO NO....because when I disconnected the amp stage my waveform reading on the oscilloscope, went way off scale, telling me whoops, can't adjust the input signal when it is coupled to the stage, No wonder it was so distorted I was driving the amp with a couple of volts signal instead of mV...

Alright that's figured out.

With 160 ohms for RB1 and the 1.8K for RB2 gives a nice VC of 6.03V.
Good bias there, but input waveform due to low Zin of divider drops the input amplitude to 100mV. pk.

So I do need to increase the divider impedance, while trying to keep the Av. as close to design values as possible, if I increase the divider impedance too far I then risk base current loading, which makes the divider voltage dependant on the transistor base current rather than the divider current itself. Again Not too good...

To be continued:

Now something else I need to consider, is that my signal generator has an Zout of around 700 ohms, so I'm trying to design this stage, which requires a lower Zin at this point and trying to use my generator with higher Zout, is going to of course cause discrepancies, so I'll have to maybe use the -20 and -40 db attenuator and see what I can do.
If that doesn't work than the best way to approach this is to just go by whatever attenuation is happening and just keep the signal waveform out of distortion, and check Voutput to make sure I'm getting the Av. that i want with no distortion.

Maybe that's what I need to do...

To be Cont.:

RB1 now = 270 ohms
RB2 now = 3K
RE1 remains at 10 ohms
RC1 = Rload remains at 200 ohms

static test:
VC = 6.14V.
VRB1 = 0.99V.

Ok with these new values for the divider resistors everything is working good, I randomely put 3 different transistors in this stage and every one gave the same input and output waveform NO distortion and the same Av.
However I will have to adjust the Av. for this stage because input signal shows 120mV. pk. and Vout is 1V. pk. Av. = 8.33
Since I don't have a whole variety of caps, to choose from to get the extra AC gain. So I'll kepp this stage at Av. of 8.

to be cont:

Calculate Zin of this stage:
Assume beta = 50 - 100 (for doing Zin calculations)
Rdiv = 247 ohms
{(RB1 // RB2) // B x RE1} approx. = (166 ohms. - 198 ohms)

Alright that's just to low, or else I'll be cascading stages all day trying to get the Av. I need.

So I will rework the values to get double than what this is right now.

with Beta chosen to be 50 :
I want Zin to be from 330 - 400 ohms
RB1 x RB2 / (RB1 + RB2) = Rdiv.
and { (Rdiv. x 500) / (Rdiv + 500)} = Zin = to {(RB1 // RB2) // B x RE1}
So { - (B x RE1 x Zin) / ( Zin - (B x RE1) } = Rdiv.
B = 50, Zin = 330
{- 500 x 330) / (330 - 500) = 970 = Rdiv. = RB1 // RB2
so 970 = (RB1 // RB2) = Rdiv.

Therefore I'll choose 1K ohms for RB1.
RB2 = { (Rdiv. x RB1) / (RB1 - Rdiv.) }
RB2 = 32.3K ohms.

Now quick voltage check calculation:
(12V. x 1K) / (1K + 32.3K) = 0.36V. Not feasable, I need 1V.

So I'll solve for RB2 using ohms law.
RB2 = 11K
I'll change these values and see if any significant change in base current loading.
RB1 = 1K
RB2 = 11K

static test:
need to make RB1, = 1.2K
VC =5.90V.
VRB1 = 1.02V.

Dynamic tests:
Shows good results as before.
Same VC and waveform input and output, with 3 different transistors.

Calculate Zin of this stage now:
Rdiv = 1081
Zin = 342 - 519 where beta is 50 -100 for calculations.
I like those Zin values.

To be cont.: ]]> hobbyist http://forum.allaboutcircuits.com/blog.php?b=373 Forgot or Lost Password http://forum.allaboutcircuits.com/blog.php?b=372 Fri, 10 Jul 2009 07:54:45 GMT If you have forgot or lost your password you can use the Lost Password Recovery Form (http://forum.allaboutcircuits.com/login.php?do=lostpw) On... If you have forgot or lost your password you can use the Lost Password Recovery Form

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Dave ]]> Dave http://forum.allaboutcircuits.com/blog.php?b=372 AC current sensor http://forum.allaboutcircuits.com/blog.php?b=366 Mon, 22 Jun 2009 00:10:49 GMT This is a tutorial on basic transistor circuit design for multiple staging.
This is a AC current sensor, based on a "radioshack" 12.6V. 1.2A, power transformer, used as the detector.
Prepararation:
Begin by taking an ordinary 60W. lamp. Wrap its cord about 4 complete turns longitudenal around transformer.
Tape tightly, I taped it then used a mini bar clamp to keep the wires tight against the Xfrmr.
Also the transformer needs to set on a small piece of steel , my bar clamp takes care of that.
I put my voltmeter at the transformer windings primary side,for AC readings and with lamp off and on .
Using a AC voltmeter I got no readings.
------------------------------------------------------------
OBJECTIVE:
Theory is that by wraping a few turns of the lamp cord around a power transformer, that when lamp is
plugged in, the current through the corde would induce a voltage into the windings of the transformer,
and by hooking the primary leads into this amp will detect and amplify the change in voltage induced,
then rectify and further amplify the signal to be used to drive a load.
CIRCUIT DESIGN:::

See schem. #1

1. This first amp will be designed for matching a very high Z of the transformer output to a rather low Z input
of the next stage where most of the amplier gain will take place.
So this first amp will be used primarily for Z matching. Therefor not as much gain is needed. (Q1 stage CE. amp)
Choose VCC = 8V.
Choose R3 = 620K which is a good high Zin.
Choose R1 = 62K so as to start bringing Zout of Q1 lower for next stage.
Choose VCQ1 to be 1/2 VCC, so VC = 4V.
Choose VCE = 2V.
Therefor VEQ1 = 2V.
Calculate R2 by equations {VCQ1 / R1) = IC and R2 = (VEQ1 / IC)
R2 = 31K make it 33K a standard resistor value.
Now (VEQ1 + 0.7V.) = 2.7V. label as VBQ1.
So (VBQ1 / R3) = 4.35 uA. label as IDQ1.
So now ((VCC - VBQ1) / IDQ1) = R4
R4= 1.2Meg. Which will be 910K and 330K in series.
Measurements and adjustments:
Static:
VCQ1 = 4.26V.
VBQ1 = 2.55V.
VEQ1 = 2.06V.
No need to change any values.
TEST:
Dynamic:
Now plug in the signal input through a 100uF capacitor at the base of Q1,
and a 100uF capacitor at the collector Q1 and check with osciloscope for any kind of wave form (60Hz.)
1.Depending on which way I looped the lamp wire around the Xtrfrmr, depends on which lead is the input
and which is connected to ground. I switched the wires around until I found a change in amplitude on my
osciloscope. I foiund for my set up that the ground wire is the side of the Xtrfrmr, closest to the wall outlet.
And the input is the side that the lamp is on.
2. The wave form shows a lot of noise, I first put C4 in the circuit to give some AC gain the noisey waveform
was amplified greatly. Then I put C3 in the circuit and that eliminated the noise and got a good 60hz. waveform
at around 10 mV. peak. With lamp off, this is the stage sensing line voltage even with no current flow through the lamp.
When I turned the lamp on I got a peak voltage of 14 mV. peak. So it increased 4mV.pk.
Now from here on out I will design this with voltmeters only.
So as to record actual volt. readings.

DATA:
lamp off = 7.6mV. rms.
lamp on = 22.6mV. rms.
OBSERVATIONS for stage Q1:
This stage is working very well, first of all no readings at the input, and at the output there is a standing
AC voltage of 7.6mV. due to sensitivity of stage to sense line voltage. When a true input comes in, lamp turned on;
then it detects this change and sends an output voltage of 22.6mV. Amplifies the change nearly 3 times.
Also good Z matching too.
How I know it is sensing line voltage, I used a battery and when lamp is UNplugged waveform shows
rf noise, when plug is in wall outlet and lamp is OFF, I get a rf noise superimposed on a 60HZ waveform.
Telling me it is sensing the line voltage and amplifying it.
　
DESIGN stage Q2:
Preliminary test,
Using a resistor sub box, switch in resistors for a load on the other end of C2 to ground.
Check for considerable decrease in amplitude of waveform with lamp on.
record the resistance value, so as to know what Zin needs to be for next stage.
Data:
20K load dosn't affect Voltage reading.
design:
So I'll choose a 47K resistor for the next stage. And work some values to get high gain as well as
nice low Zout to drive the next stage.
Choose R7 to be 1/10 of R8 which is 4.7K, and make R6 27K to give a Av. around 5 (dc gain).
Calculations:
VCQ2= 4V.
VEQ2= 696mV.
VBQ2= 1.396V.
so R9 = to around 220K.
Measurements and adjustments:
Static:
VCQ2=3.76V.
VEQ2=0.75V.
VBQ2=1.36V.
No need for adjustments.
TEST:
Dynamic:
DATA:
Lamp off =705mV. rms.
Lamp on = 1.68V. rms.
　
DESIGN stage Q3:
Preliminary tests:
Now that I have enough volt output to bias a diode
Vpk. Lamp off = aprox. 1V.
Vpk. Lamp on = 2.37V.
So I have enough output voltage pk. to bias a diode for rectification, and filtering.
But first I need to bring the Zout of this amp low enough to run a load.
So I'll work it towards around 470 ohms, Zout.
To go from 27K to 470 ohms, I'll need a Common Collector amplifier arangement.
Design last stage for low Zout.
Assume Beta, to be around 100
I will also remove the capacitor and direct couple this stage to Q2.
Now I need to work some values to give me the least signal loss at the input of Q3,
but to have the smallest possible Zout at the emitter of Q3.
VEQ3 = 3V because VCQ2 = 3.76V. measured value.
　
Now add the rectification filter D1,R14,C5
R14 ia made variable to adjust for different loads.
.
TEST DC Vout.: (no load)
Vout Lamp off = 1.56V..
Vout Lamp on = 1.86V.
　
TEST with LED load::
Vout Lamp off = 1.28V.
Vout Lamp on = 2.03V.
LED'S work good with R14= 3K ohms.
　
CONCLUSION:
Overall circuit works ok.
This was designed using my benchtop variable power supply, 8V.
I made it to work with 9V. battery.
This will work at supply voltages from 7 - 12 Volts.
It works well with a 9 volt. battery.
When first turn on the circuit it takes a little bit for every thing to work properly
but once it's left hooked up to the battery it works fine.
C6 keeps the circuit from oscilating due to battery impedances.
But this could work better, so I will rework the output stage and add some
additional stages to give a good volt. output that's more predictable.
--------------------------------------------------------------------------------------------------------------------------
REDESIGN :::::
See schematic # 2:

First I will unplug the lamp and deal with the RF signal noise at the beginning input.
Using my osciloscope I found that 33uF is good to get rid of noise.
C3 takes care of that.
Stage Q1:
Dynamic test: (no load)
VCQ1, lamp off = 8.4mV. rms.
VCQ1, lamp on = 26.6mV. rms.
　
Stage Q2:
Dynamic test: (no load)
Needed to put C5 in the Q1 stage because of eratic readings. Probably oscilations.
VCQ2 lamp off = 283mV. rms.
VCQ2 lamp on = 607mV. rms.
Design stage Q3:
Choose R12 to match R6 at 27K.
Choose R10 to = 4.7K, to bring Zout down further.
Choose Av. = 4 so R11 = 1K
Calculate R13 to be 110K.
Calculated voltages:
VCQ3 = 4V.
VBQ3 = 1.55V.
VEQ3 = 0.85V.
Measured values:
VCQ3 = 4.15V.
VBQ3 = 1.5V.
VEQ3 = 0.85V.
no need to change values.
Dynamic Test:
VCQ3, lamp off, = 1.77V. rms.
VCQ3, lamp on, = 3.2V. rms.
Very Good Av. and response from lamp off to lamp on, condition.
Also the circuit is more stable and predictable on Vout. rms.
　
Design Q4 stage:
Q4 will be a common collector amp config. to give required Zout neccesary, to drive a load.
So I'll choose R14 to be 470, assuming a Beta of 100 for Q4 would give a Zin around 47K.
So as to not load the Q3 collector so heavily with Q4's bias base current.
.I should have a little over 3V. at the emitter of Q4.
Static measurement. = VEQ4 = 3.5V.
Dynamic test:
VEQ4, lamp off, = 3V. rms.
VEQ4, lamp on, = 3.4V. rms.
Not good, with the Q4 stage direct coupled to Q3, caused Q3 to saturate the standing voltage.
So a change in input, lamp on, showed no significant change at VEQ4.
So I'll capacitive coupling between these strages, and bias Q4 with as high Zin possible, keeping Zout low.
Choose VEQ4 to be at 4V. And make R16 10 times larger than R10, = 47K.
Calculate R15 = 33K.
Calculations:
VEQ4 = 4V.
VBQ4 = 4.7V.
Measured values:
VEQ4 = 3.33V.
VBQ4 = 4.02V.
This is off because of the base loading effect due to low emitter resistor.
But for this application it will work.
Dynamic test:
VEQ4 = 3V. rms.
So this approach will not work. Either..
With Q4 in the circuit the VCQ3, rises to saturation on the standing voltage,
when I remove Q4 than VCQ3 goes back to normal.
I need to work with Q4 so as to keep it from interacting back to Q3.
Tests show that if I raise R14 to around 3K then the VCQ3 is working normal. (1.4V rms.)
(there's a small drop compared to 1.77V rms. of original value due to Q4 loading Q3.)
R14 is now changed to 3K. Also direct coupling can now be done.
Dynamic test:
VCQ3, lamp off, = 1.40V. rms
VCQ3, lamp on, = 2.07V. rms
VEQ4, lamp off, = 1.47V. rms.
VEQ4, lamp on, = 3.12V. rms
So far, a very small change in voltage that the transformer, detects, from sensing voltage,
to having voltage induced due to line current flowing to the lamp, was so small that it could not be,
measured with my meters.
But now this circuit amplifies the standing (non current) voltage sensed at the outlet, and the change in
voltage when current flowing to lamp, by amplifying this change by twice the amount.
(NOTE): I've learned that a common collector amp. can't just be thrown in with the smallest Zout desired
without careful testing and measuring, voltages at the previous stage, to make sure that the CC amp,
is not causing heavy loading, thereby ruining the signal coming into it.
Now it works properly at this stage.
Now that it's not in the milivolt region anymore, then I can no longer use small signal amps, because
the amp would be driven into saturation at the standing (sensed) voltage, and no change could be detected.
So now it's time to rectify and filter it to give a DC signal to work with for amplification and eventually switching
on a load.
Design rectifying and filter:
Through experimenting, C10 is good at 1nF.
Test DC Vout:
VEQ4, lamp off, = 3.94V
VEQ4, lamp on, = 5.6V
Around 1.5V. increase, this will be a good signal to work with.
------------------------------------------------------------------------------------------------
Now Design of the DC amplifier:
I start more at the output and worked my way back to the rectifier stage, that way I can ensure
a low Zout and increase in Zin at each stage going back.

Refer topicture #3

See schematic #4

Stage Q5 DC amp
Choose R18 = 470 ohms.
Make Av.=10
That makes R19 = 47 ohms.
Choose VCQ5 = 4V.
Choose R16 A = 1k. (20 times > than R19)
Calculate R15 = 6.2K.
Test voltages showed good values.
Design stage Q6:
Stage Q6 will DC couple into Q5
Replace R16 A with stage Q6.
Calculate VBQ5, this will become VCQ6.
Then choose VEQ6 to be 1/4 of this value.
Calculate current through R16 A, and solve for new resisor value R16 B.
Then usual calculations solve for R17 and R20 A.
Test measurements showed good values.
Design stage Q7:
Stage Q7 will DC couple into Q6, replacing R20 A
Choose R20 B to be 1/3 of R20 A, and solve for current through R20 A.
This current value will be the collector current for Q7.
Usual calculations solve for R21 and R22.
Test measurements showed good values.
Now I have a high Zin at the input of this DC amp Q7 base input.
And a somewhat low Zout at the output of this DC amp, VCQ5, or VEQ5.
The base current is still having some effect on the DC rectifier circuit, so keeping with
BJT. I'll work the base input of Q7 to give more Dc gain to the input signal.
　
So I'll start with replacing R21 A with another amp stage, and use a 47K for emitter resistor.
Call that R21 B. Now calculate the current through R21 A and solve for ICQ8. = 38uA.
Now ( 38uA x 47K) = VEQ8 = 1.78V. + 0.7V = VBQ8 = 2.48V.
Choose another 100K for R23, and solve for the other bias resistor. Calculates out to 220K.
However due to high resistance values and sensitivity of the circuit at this stage I had to use
R24, R25, R26, to adjust values to get the desired VCQ5 back to it's nominal designed value
of around 4V.
Now everything is working good for static measurements of all bias voltages.
The AC amp is not yet connected, now I need to make another stage to take a positive input
from the rectifier and give a input to this DC amp. Because right now an input to the DC amp will
give an inverted output.
Now I tested with a 9Meg. resistance from positive supply to the emitter of Q8 and got a significant
response of VCQ5 going from 4.3V to around 6.5V. which means is one more amp preferably a
common collector amp inputing to the emitter of Q8, should give me all the High Zin needed to not load
the AC amp, as well as all the signal transfer needed to switch the DC amp to a relatively high Vout..
　
Design Q9 stage:
This was all done with experimentally switching resistors in and out until I got the proper VCQ5 at idle conditions.
Then switching the lamp on gave me a jump in voltage at VCQ5, neccesary to drive a load.
Lastly I hooked up the LED to the output and the entire circuit works perfect.

See final circuit schematic #5

-----------------------------------------------------------------------------------------------------
CONCLUSION:
When I first apply power to the circuit wether power supply or Battery, the LED lights
momentarily, then shuts off, it takes a good 30 secomds for everything to get into
equilibrium before the circuit is ready for use, but after that, I can turn the lamp on and
the LED will light up nice and bright, and stay lit as long as the lamp is on,
then turn lamp off, and LED turns off. This could be used to drive an opto isolater, so
as to drive a relay or something.
Overall this circuit was designed using BJT. only, and learning how to design by matching impedances,
and transfering AC signal through stages, then converting to DC and amplifying that signal, through
stages until the signal has enough strength to drive a particular load.
I designed it using my power supply set at 8V.
I varied the supply to find the min, max, volt. it would work at:
Results are, ( MIN> 5V. @ MAX> 12V. )
Good range of supply voltages for it do work at.
This circuit provided many challenges in impedance matching, and signal preserving, as well as amplifying.
I realize that this could have been designed a lot more simpler with less components, and different take on it,
but I wanted to design it working through the problems that are encountered and learning how to solve
those problems.
　
This circuit was more or less a excersise in problem solving when designing a circuit.
　
　
　

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]]> hobbyist http://forum.allaboutcircuits.com/blog.php?b=366 <![CDATA[The "Unus" project (part 2)]]> http://forum.allaboutcircuits.com/blog.php?b=365 Sun, 21 Jun 2009 12:43:31 GMT Here are some pictures of the assembled PCB. Enjoy! Attachment 165 (http://forum.allaboutcircuits.com/attachment.php?attachmentid=165) Front ... Here are some pictures of the assembled PCB. Enjoy!

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Copper side ]]> cumesoftware http://forum.allaboutcircuits.com/blog.php?b=365 Ignition circuit on an old motorcycle http://forum.allaboutcircuits.com/blog.php?b=339 Sat, 16 May 2009 06:25:29 GMT In January of this year I bought an old motorcycle, a 1946 Harley Davidson WL. This is a civilian model of a motorcycle that HD made several hundred... In January of this year I bought an old motorcycle, a 1946 Harley Davidson WL. This is a civilian model of a motorcycle that HD made several hundred thousand of during WW II. The engine has two cylinders displacing 45 cu. in., in what they call a "side-valve" configuration, what I've always called a flathead.

Being that this forum is concerned with electronics and such, I thought that some readers might be interested in how the ignition circuit works on this old beast.

On the right side of the engine is a component that looks something like a distributor, but unlike most car distributors, there are no spark plugs attached. The unit has a set of points and a capacitor inside, just like older car distributors, but unlike them, there are no spark plug wires attached to it. It's also referred to as a timer, or circuit breaker, rather than a distributor.

The ignition circuit is pretty simple. The primary circuit consists of the the battery, coil, and timer. The secondary circuit consists of the coil and the two spark plugs. When the engine is running (or when you're starting it), the timer rotor turns, and its two lobes cause the points to open and close at specified times related to crank and valve position. When the points close, current flows through the primary circuit, which induces a current in the secondary windings of the coil, and across the gaps of both spark plugs. When the points close, the electric field in the coil collapses.

By firing both spark plugs whenever the points close, they didn't need to distribute the spark to an individual plug, and this is why there aren't any plug wires coming out of the timer. The disadvantage of creating a wasted spark for a cylinder that isn't ready to fire is a weaker spark on the one that needs it, but hey, that's the way the engine was designed. ]]> Mark44 http://forum.allaboutcircuits.com/blog.php?b=339