555 Function Generator

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
OK, I am picking this thread back up, after moving it to match the changes to AAC.
 
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Thread Starter

Wendy

Joined Mar 24, 2008
21,847
It is frustrating This circuit came so close to doing what I wanted if I could have done it with LM324s I could do it with any op amp. Ba ck to the drawing board ,I suspect the problem is shoot through.
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
OK, one of my college instructors once staid skull sweat is cheaper than hardware. On this project I have taken it to heart. I accidentally overwrote this file once with a trash file (ARGGGGGH!) and restarted from scratch. I figure it has taken two weeks of 8 hour days to get here. I have tried to use every bit of feedback from the previous failure.

555 fG V21.png

There is a lot more to this post coming so be patient.Ok BG Micro website:
http://www.bgmicro.com/

Parts list
Qty 1 9V Battery
Qty1 9V Battery Clip(BG Micro P/N BAT1098)
Qty 1 Protoboard (BG Micro P/N ACS 1563)
Qty 1 U1 TLC555 CMOS IC (BG Micro P/N IC STL C555)
Qty 3 U2, U3, U4, NJM4576 fast Dual Op Amp(BG Micro P/N ICS 4515)
Qty 2 CR1, CR2, 1N4454 Small signal diodes or equivalent (BG Micro P/N DIO1053)
Qty 1 C3, 220 uF 16 V Capacitor (BG Micro P/N CAP1018)
Qty 3 C1,C2,C4 0.1uF Capacitor (BG Micro P/N CAP1255)
Qty10 R1, R2, R4, R5, R6, R7, R8, R10, R12, R15, 10KΩ 1/4W 5% Resistor
Qty 1 R3, 100 KΩ Variable Trimmer Resistor (BG Micro P/N RES1502)
Qty 1 R13, 10KΩ Variable Trimmer Resistor (BG Micro P/N RES1420)
Qty1 R6, 4.7 KΩ 1/4W 5% Resistor
Qty1 R9, 2.2KΩ 1/4W 5% Resistor
Qty 1 R11 15KΩ 1/4W 5% Resistor
Qty1 R14 6.2KΩ 1/4W 5% Resistor

OK C1 is the range selector. Using the formula f=.7/(C1 R4) here are the values for C1 I'll be trying:
7pf=1MHz
70pf=100KHz
700pf=10Khz
7nf=1K Hz
70nf=100Hz
.1uF=70Hz

Of course this is part of the experiment.

Given my rate of recovery I guesstimate it will be a year before I try this out. If some one does it first please share your results
 
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be80be

Joined Jul 5, 2008
1,927
Wounder how well it would work with a 555 I don't have a 7555
Not having much luck with this too NJM4576
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
They are relatively cheap an fun to use. I was planning to try a 555 as as drop in replacement later.
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
Pitfalls: You may have to audition diodes if they are not matched it can cause some asymmetry in the sine wave (discovered this on first set of experiments.). C1 can not be polarized as the signal around it swings both plus an minus( given the low values, a minor issue).

In case you haven't figured it out you are dealing with a girl with way too much time on her hands. I really didn't want to retire dang it!
 
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dl324

Joined Mar 30, 2015
8,855
I really didn't want to retire dang it!
Welcome to the party...

A lot of people who retire early didn't want to retire early. Some 20 year old girl made the decision for me when she t-boned me and gave me a back injury that looks like it'll be permanent.
 

Moritz

Joined Jun 4, 2018
7
I tried building it, it was a nightmare.
blew up a 555, because I used +-15V supply for the opamp.
I don't know if it is appropriate to post this here, but I ended up redesigning the circuit to reduce the number of opamps in the feedback loop while retaining the shared capacitor. it still only uses a single cap for both the integrator and the 555. the feedback on pin 5 is for better stability.
Untitled999.png
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
CMOS ICs are rated to 18VDC. I am very conscious of power supplies when I design. The op amps were well within their operating range in my design. So why not try it the way I designed it?
 

Moritz

Joined Jun 4, 2018
7
in my area I can only get the ne555 and I wanted the output to be the max, what happened was that the opamp was to slow for the frequency and it puled high at around 1MHz, 555 heated up and gave off a funny smell, the redesign is so that even if one of the ic`s run out of range it won't pull high or low it will just keep occilating at max frequency of the combined circuit
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
Very few op amps do rail to rail My design goal was to have the same approximate output level if you switched the wave forms. Frankly I was trying to add more drive but I ran out of protoboard space.

Differentia Powerl Amp.png
 

Moritz

Joined Jun 4, 2018
7
when you say drive do you mean current?
and ja the reason I wanted to try your circuit is so that I won't have to change the RC for both the trigger and the integrator.
the circuit above still works on the same concept as your original circuit the triangle waveform retains its level over all (possible) frequencies.
 

Moritz

Joined Jun 4, 2018
7
*not the circuit above but the one in #70
your circuit above only increases the possible current draw, I wanted to increase the voltage to 30V(p-p).
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
Thank you I did this correction once but with all the fluff in between my ears I missed one copy.

*not the circuit above but the one in #70
your circuit above only increases the possible current draw, I wanted to increase the voltage to 30V(p-p).
You could use a 15Vpower supply, no +/- needed. and feed the output into a separate amp to get the desired amplitude, I worked very hard for minimum parts count. to get more performance you will need to add more parts.
 

Thread Starter

Wendy

Joined Mar 24, 2008
21,847
Actually I took a second look The output needs to sink as well as source current I made a similar mistake an the other side, which is what I was thinking had happened. I am in the process of creating another experiment using this design. I am the first to admit I don't always get it right.
 

Moritz

Joined Jun 4, 2018
7
can someone help me?
input=
Untitled5.png
circuit=
Untitled4.png
output=
Untitled3.png
it is only noisy when its positive
and the square wave and the triangle wave are fine it's only the sine wave that's doing this
 

Audioguru

Joined Dec 20, 2007
11,251
Your output transistors are biased OFF during the oscillation part of the waveform. Don't you want the output transistors to be biased in class-AB?
The 1N4003 diodes are designed as rectifiers for 50Hz and 60Hz so they are very slow. Your diodes are in series with the bases which is bad.
Please make the output transistors in class-AB. Unmatched transistors in parallel without emitter resistors is also bad. If you use them for power then use a power amplifier IC instead.
 
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