As usual, you are correct

I did a test run and my LED stayed on (I have an LED cathode connected to sigout), even when the sigin was generated by the ECU.

The sigin is a PWM signal, but I had previously made a flattener with a 10k resistor and a 1uf capacitor ... that doesn't seem to be working correctly with this new circuit though.

As verification, I brought a 14v (straight from battery/alternator) signal straight to R1 and the LED turned off.

 

You made no previous mention of this "flattener", which more correctly would be called a low-pass RC filter.

You might require a voltage follower from the input. I have no idea what your signal level is.

 

Ok, with my DMM, here is what I got while on the test bench (LED cathode is connected to sigout)


Signal input voltage at 4.77v, LED On
Before R1 - 4.77vDc
After R1 - 0.62vDc
Before R2 - 13.77vDc
After R2 - 0.71vDc
Before R3 - 13.77vDc
After R3 - 0.009vDc
Before R5 - 0.001vDc
After R5 - 0.62vDc



Signal input voltage at 5.12v
Before R1 - 5.12vDc
After R1 - 0.63vDc
Before R2 - 13.77vDc
After R2 - 0.113vDc
Before R3 - 13.77vDc
After R3 - 13.77vDc
Before R5 - 0vDc
After R5 - 0.63vDc



R1 is what effects voltage, or R5? I disconnected R5 and voltage after R1 (aka Q1 base) went from 0.631vDc to 0.652vDc.

I see that when I adjusted voltage down to 4.5vDC and put a 20 turn 10k potentiometer in place of R5, it finally turned the LED off when down to 250ohms. Does that sound correct?

 

I tried it with and without the flattener, first without the flattener, it was just an afterthought from a related circuit I was trying to build before

You made no previous mention of this "flattener", which more correctly would be called a low-pass RC filter.

You might require a voltage follower from the input. I have no idea what your signal level is.

 

OK.
Go back and use the circuit I posted in reply #44, but add the 1uF cap between the comparator input and ground.

 

Will do, I'd imagine it's going to be a while before I have a result as I don't have any of those components and Radio Shack doesn't appear to carry them all, which means internet order and shipping time.

OK.
Go back and use the circuit I posted in reply #44, but add the 1uF cap between the comparator input and ground.

 

Sgt,

Out of the search on this page
http://mouser.com/Search/Refine.aspx?Keyword=lm2903
the part number 755-LM2903DT had a very wide operating temperature, so I believe that's my best choice, do you agree? I'm going to order 10 of them if so.

Is there any other very common components that you'd recommend I order so that I have some on hand? (keep in mind that 90% of anything I build will be for an automotive environment and voltage/amp values)

 

Is there any other very common components that you'd recommend I order so that I have some on hand? (keep in mind that 90% of anything I build will be for an automotive environment and voltage/amp values)

http://www.jameco.com/webapp/wcs/st...ine=1&langId=-1&catalogId=10001&storeId=10001

 

Believe it or not, I'm changing the circuit a bit.

See the attached.

R3 could be replaced by a 2.5k resistor between the junction of R2/D1 and the inverting input of U1, a 7.5k resistor from the inverting input of U1 to ground.

The inverting input of U1 should measure right about 4v. The exact voltage is not important; just as long as it's constant. R2 and Zener diode D1 should take care of that.

R6/C1 represent your "flattener", which is more correctly called a low-pass RC filter. (If you say "flattener", nobody will know what you are talking about.)

R5 is a 100k Ohm 10- or 21-turn trimmer potentiometer. This provides adjustment for when your comparator output will trip.

R4 still provides hysteresis for the comparator. This prevents the comparator from switching numerous times if the input signal has a slow rise or fall time.

 

Parts are due to arrive on Monday ... I was hoping for tomorrow

Updates soon to come, thanks again Sgt

 

Finally got some time to look at my parts, I'm pretty disgusted, look what came in the mail, I don't know how I'm supposed to use these?

I'm not sure what I did wrong, but I'm pretty frustrated none the less

 

Ugh - you ordered the 755-LM2903DT? That's an SMT/SMD device.

You'll need to make a circuit board to mount it on - but you were going to have to do that anyway, right?

 

OK, tell me about the other components you have on hand. Are they 1/4W axial resistors?

How about D1, the 1N751 - it's an axial lead Zener, right?

And C1 - is it radial or axial? Link to the page where you bought it from, please, or just the size of it.

I'll also need the info about R5, the 10k pot, and R3, the 10k pot. Are those panel mount pots, or trimmer pots that are meant for PCB mounting? If the latter, I'll need the part numbers.

 

Sorry to jump in on this thread off topic.

But... having scanned through briefly, I think this thread pays testament to what this site is about; one person very willing to put the time and effort into learning, and another (others) equally willing to mentor and teach.

Fair play to you both! Thumbs up.

 

Sorry to jump in on this thread off topic.

But... having scanned through briefly, I think this thread pays testament to what this site is about; one person very willing to put the time and effort into learning, and another (others) equally willing to mentor and teach.

Fair play to you both! Thumbs up.

Unfortunately, it's a bad example of what happens when sufficient questions about what the original poster is actually trying to do are not asked.

While the discussions about transistors were obviously a learning experience for gte (and hopefully other members will benefit as well), the amount of time and number of posts that it's taken to get from the first question to the present state of affairs has been a rather long trek indeed.

It's unfortunate that I missed gte's question about the particular LM2903's he was purchasing; there are only so many hours in a day, many other people have projects they need help with, and believe it or not - I have a life, too.

It's not a complete disaster that he purchased SO-8 packaged IC's instead of DIP-8; they'll work just fine on a circuit board - it's just that breadboarding would be a chore.

 

I'll get the parts list

So anything labeled SMT/SMD is for PCB's only?

I will post a parts list, doh I'm an idiot! Thank you for your patience!

OK, tell me about the other components you have on hand. Are they 1/4W axial resistors?

How about D1, the 1N751 - it's an axial lead Zener, right?

And C1 - is it radial or axial? Link to the page where you bought it from, please, or just the size of it.

I'll also need the info about R5, the 10k pot, and R3, the 10k pot. Are those panel mount pots, or trimmer pots that are meant for PCB mounting? If the latter, I'll need the part numbers.

Unfortunately, it's a bad example of what happens when sufficient questions about what the original poster is actually trying to do are not asked.

While the discussions about transistors were obviously a learning experience for gte (and hopefully other members will benefit as well), the amount of time and number of posts that it's taken to get from the first question to the present state of affairs has been a rather long trek indeed.

It's unfortunate that I missed gte's question about the particular LM2903's he was purchasing; there are only so many hours in a day, many other people have projects they need help with, and believe it or not - I have a life, too.

It's not a complete disaster that he purchased SO-8 packaged IC's instead of DIP-8; they'll work just fine on a circuit board - it's just that breadboarding would be a chore.

 

eng1ne, you are completely right. This thread is quite a testament to Sgt's character and willingness to help.

As part of my learning, I've definitely said the wrong things, or not said enough, and he's been very patient with me, shows what a nice guy he is.


On a positive note my electronics course starts tonight and I should be less of a burden after this class


ELECTRONICS
ELEC Linear Electronics
(4 credits)
In this course the student will learn the characteristics
of electonic devices, such as diodes,
transistors, and operational amplifiers, and their
behavior in various electronic circuits. Specifically,
applications of the following devices will
be studied: rectifier diodes, zener diodes, bipolar
junction transistors (BJT), field-effect transistors
(FET). Also, various applications of the
operational amplifier will be studied.
PRQ: ELEC-107
EVENING:
2256 550 7:30PM-10:20PM T
6:00PM-9:00PM TH

Sorry to jump in on this thread off topic.

But... having scanned through briefly, I think this thread pays testament to what this site is about; one person very willing to put the time and effort into learning, and another (others) equally willing to mentor and teach.

Fair play to you both! Thumbs up.

 

I'll get the parts list

Good.
For some of the items, I can simply go by size; like 1/4W resistors, etc.
Thru-hole resistors generally have axial leads - one lead coming out of each end of a cylindrical or dumbbell-shaped body.

Thru-hole capacitors can either have axial leads, or radial leads. Radial leads are when both come out of one end. With axial lead components, the length of the body is the important item. With radial lead items, the spacing between the leads at the body is the important item.

So anything labeled SMT/SMD is for PCB's only?

Well, they can be used in breadboarding - however, you really need an adapter such as this one:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=309-1098-ND
Either that, or you'll have to try to solder wires onto each lead, which is a pain.

I will post a parts list, doh I'm an idiot! Thank you for your patience!

You're not an idiot - you're just new at this, and bound to make mistakes. As long as you learn something, and the mistakes aren't dangerous or costly, then it's worth it.

Sorry that I didn't catch your question about it before you ordered. I've had a good bit on my plate lately, and there just isn't enough time to get everything done.

 

On a positive note my electronics course starts tonight and I should be less of a burden after this class


ELECTRONICS
ELEC Linear Electronics
(4 credits)
In this course the student will learn the characteristics
of electonic devices, such as diodes,
transistors, and operational amplifiers, and their
behavior in various electronic circuits. Specifically,
applications of the following devices will
be studied: rectifier diodes, zener diodes, bipolar
junction transistors (BJT), field-effect transistors
(FET). Also, various applications of the
operational amplifier will be studied.
PRQ: ELEC-107
EVENING:
2256 550 7:30PM-10:20PM T
6:00PM-9:00PM TH

Sounds good!
Have you taken the prerequisite course, ELEC-107?
If not, you may find yourself in a bit over your head.

To keep yourself from getting behind and feeling "lost", you'll need to read through our E-books; Vol. I and Vol. II - links to the E-books are at the top of every page on this site.

 

Line No. Product Detail Customer Part # Order Qty. Shipped Qty. Pending Qty. Price
(USD) Ext.
(USD)

1 Mouser #:581-TAP105K035CCSMfr. #:TAP105K035CCSDesc.:Tantalum Capacitors - Solid Leaded 35V 1.0uF 10%
5 5 0

$0.40​

$2.00​

2 Mouser #:598-SK010M063STMfr. #:SK010M063STDesc.:Aluminum Electrolytic Capacitors - Leaded 1uF 63V
20 20 0

$0.10​

$2.00​

3 Mouser #:299-330K-RCMfr. #:299-330K-RCDesc.:Carbon Film Resistors 330Kohms 5%
10 10 0

$0.05​

$0.50​

4 Mouser #:660-MF1/4DC3901FMfr. #:MF1/4DC3901FDesc.:Metal Film Resistors 3.9K 1% 100PPM
20 20 0

$0.06​

$1.20​

5 Mouser #:299-100K-RCMfr. #:299-100K-RCDesc.:Carbon Film Resistors 100Kohms 0.05
20 20 0

$0.05​

$1.00​

Good.
For some of the items, I can simply go by size; like 1/4W resistors, etc.
Thru-hole resistors generally have axial leads - one lead coming out of each end of a cylindrical or dumbbell-shaped body.

Thru-hole capacitors can either have axial leads, or radial leads. Radial leads are when both come out of one end. With axial lead components, the length of the body is the important item. With radial lead items, the spacing between the leads at the body is the important item.


Well, they can be used in breadboarding - however, you really need an adapter such as this one:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=309-1098-ND
Either that, or you'll have to try to solder wires onto each lead, which is a pain.


You're not an idiot - you're just new at this, and bound to make mistakes. As long as you learn something, and the mistakes aren't dangerous or costly, then it's worth it.

Sorry that I didn't catch your question about it before you ordered. I've had a good bit on my plate lately, and there just isn't enough time to get everything done.