Home
JAQForum Ver 20.06
Log In or Join  
Active Topics
Local Time 01:15 16 Jun 2021 Privacy Policy
Jump to

Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.

Forum Index : Electronics : Circuit to flash one LED then the other at about a second each.

     Page 3 of 3    
Author Message
bob.steel
Regular Member

Joined: 27/02/2020
Location: United Kingdom
Posts: 59
Posted: 06:23am 12 Jun 2021
Copy link to clipboard 
Print this post

Starting to think I'm the victim of a close knit leg pulling joke group actually.Ha Ha .
Seriously though can anyone suggest some voltage test points I can probe for . I don't understand the operation of the circuits when you say components are doing double duty . I would like to understand that.

Ive spent days now trying to get this circuit to work and it won't .
Position is it flashes right led briefly then turns the left led on hard turning the right off.

As good as I can do .

Here it is on a breadboard , lets see if you can find a fault .





Another one a little later when inet not clogged here.
Edited 2021-06-12 16:39 by bob.steel
 
Warpspeed
Guru

Joined: 09/08/2007
Location: Australia
Posts: 3939
Posted: 07:20am 12 Jun 2021
Copy link to clipboard 
Print this post

  bob.steel said  Starting to think I'm the victim of a close knit leg pulling joke group actually.Ha Ha .


Definitely not !

I have had similar problems with my solar hot water heater circuit.  I suggested a circuit, built it, tested it, even had boards made that I supplied fully loaded and tested.  But some people have never been able to make it work.  I have no idea why that is so, it works fine here.

I have no idea what the problem is, but its an uncomfortable situation for both yourself and Mike.
Cheers,  Tony.
 
wiseguy

Guru

Joined: 21/06/2018
Location: Australia
Posts: 598
Posted: 07:57am 12 Jun 2021
Copy link to clipboard 
Print this post

That was a good idea to send the picture. What are the small transistors are they the  C2655 - it looks like you have wired it as if they were 2N3904's ?

If they are C2655's swap the green and blue wires on both small transistors and try again. (ie blue to the centre green to outer).

If it gets too hard, maybe Ill go build mine again and take a picture of it.

The more than 1 function comment is described a bit better below:

The current limit resistors (3K9 on your board) for the FET gates are also the collector resistors for the multivibrator bipolar transistors. The zeners allow the 2 gate capacitors to charge when the transistor connected to its gate is on (they are forward biased  ~0.65V) and then hold the gate voltage to the value of the zener voltage when the transistor is off.  The 2 x bipolar transistors act as a multivibrator pair and also alternately control the connected FET to be on and off.
Edited 2021-06-12 20:05 by wiseguy
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
bob.steel
Regular Member

Joined: 27/02/2020
Location: United Kingdom
Posts: 59
Posted: 09:28pm 13 Jun 2021
Copy link to clipboard 
Print this post

No joy there . ive tried it a few ways with a few transistors and a few Mosfets . It doen't work and I often get both led's on at the same time .
I'm convinced its not going to work .

If you build it again what might help is a few expected voltages on points of the circuit to check against Then if I'm not getting those I can track down my errors.

I'm good at this . I built Forrest Mimms version on a breadboard and it worked fine but then I took the voltage over 20v and the mosfets died I think .I'll have to get something sorted soon.
 
wiseguy

Guru

Joined: 21/06/2018
Location: Australia
Posts: 598
Posted: 08:28am 14 Jun 2021
Copy link to clipboard 
Print this post

  bob.steel said  
"It doen't work".
"I'm convinced its not going to work".

That is taking this on with totally the wrong mindset.

It DOES work !        See here

One of the first things I learned in electronics is hmmm its not working - where did I stuff up.

When it didnt work when I built it a second time I tested the transistors, one of the 2N3904's gave this reading from my tester:

another one gave this better reading:


I wired it up as the following schematic with voltages shown,
note that C3 & C4 are not wired up yet:


Voltage readings are the same for both sides. When C3 & C4 are connected the LEDs should begin to flash - when its working voltage readings are now useless - they are all in motion/unstable.

Final wiring:


If you havent got a component tester I highly recommend one they are ~12$  from Ali.
I recommend be very cautious buying semiconductors from any Ali source I have had lots of counterfit crap sent to me. A few cents saved = a few hours wasted.

The component values are not critical to get it working, the 3k9s can be as high as 22K and the 180Ks can be from 100K - 270K Zener can be from 12V to 18V so don't get hung up on copying the schematic exactly.

At this point I cant help any further - you need to attack it with a fresh mindset and known good parts.
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
wiseguy

Guru

Joined: 21/06/2018
Location: Australia
Posts: 598
Posted: 08:48am 14 Jun 2021
Copy link to clipboard 
Print this post

Component tester link:
https://www.aliexpress.com/item/4000357301057.html?spm=a2g0o.productlist.0.0.742033e3iQOPC6&aem_p4p_detail=202106140141525615624926838730016732013

component tester case link :
https://www.aliexpress.com/item/1005001292559487.html?spm=a2g0o.productlist.0.0.1556399dNXeey6&algo_pvid=6442513a-3648-4cbf-bb49-1205949d728b&algo_exp_id=6442513a-3648-4cbf-bb49-1205949d728b-0

Total price including shipping is now closer to $20, shop around it may be cheaper.
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
Pete Locke
Senior Member

Joined: 26/06/2013
Location: New Zealand
Posts: 150
Posted: 08:55am 14 Jun 2021
Copy link to clipboard 
Print this post

Hello Bob.
If you have a basic digital multi meter with a diode test option, it's easy to verify the pin outs of bipolar transistors. Assume it's an NPN transistor as per the circuit. The positive lead of the multi meter will go on the base. You will get slightly different readings when you put the negative lead of the meter on the collector, and then on the emitter. The higher of the two readings is the emitter, and the lower is the collector. It's not a big difference. As an example you may see 0.655 indicated measuring base to collector, and 0.658 indicated measuring base to emitter. Depending on your meter the numbers may be different from the examples, but there is always a difference between the collector and emitter.
Chers
Pete'.
 
bob.steel
Regular Member

Joined: 27/02/2020
Location: United Kingdom
Posts: 59
Posted: 09:15am 14 Jun 2021
Copy link to clipboard 
Print this post

Thanks for that . with some working voltages I should be able to find the fault.
The component tester looks handy.I'll get one of those.

Thats not much difference at all Pete. Nver looked at them that way . My system is make sure there is a diode reading either side and none when neg on base.

The mindset is not the problem . Doing the same thing over and over and expecting a different result is the problem . It leads to madness so you have to jump out of it . Getting working expected voltages at set points gives me a fresh approach .

When I start my drill and compressor on the Inverter I use an inrush resistance in series with the line . 5 ohms seems to work well but I use 10 ohms ,2 devices in series on some.
Edited 2021-06-14 19:29 by bob.steel
 
wiseguy

Guru

Joined: 21/06/2018
Location: Australia
Posts: 598
Posted: 09:27am 14 Jun 2021
Copy link to clipboard 
Print this post

Peter is correct, for ~ 30 years I have tested FETs and Transistors with just a DVM on the diode test function and my tongue for confirming/testing gain....lol.

But since buying this tester I have never looked back it gives NCH/PCH, NPN/PNP, gain, pinout and also tests inductors capacitors diodes all in a few seconds. I have found it cuts down my time to identify & assemble something that usually works first time considerably.

I used it to confirm the first transistor, but not using it for the second transistor wasted ~ 15 minutes of my time - I assumed (Wrongly!) it was a good one being brand new.
Edited 2021-06-14 19:28 by wiseguy
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
bob.steel
Regular Member

Joined: 27/02/2020
Location: United Kingdom
Posts: 59
Posted: 08:35am 15 Jun 2021
Copy link to clipboard 
Print this post

Well with your help I got the transistors worked out . 2 of my new 2955's were shot and the replacements I had were different pinouts so I got new 2955's and checked them and put them in . Now at least the LED's are off . Now to work on the mosfet side and check the voltages .

I ordered one of those component checkers too today.How do you check the gain with your tongue though?
Edited 2021-06-15 18:37 by bob.steel
 
wiseguy

Guru

Joined: 21/06/2018
Location: Australia
Posts: 598
Posted: 10:22am 15 Jun 2021
Copy link to clipboard 
Print this post

  [ said  QUOTE=bob.steel
How do you check the gain with your tongue though?


I was really hoping no one would ask - but since you did. Actual gain of course remains unknown but can be reliably determined to be bugger all or quite a lot.

With the T092 pack, transistors pins 1 & 3, usually E & C are sometimes reversed (or even worse).  A transistor still has a bit of gain with C & E reversed but MUCH lower.

The resistance of my tongue is typically 50 - 150K.
So after using the diode test to determine/confirm which lead is the base I set about determining which pins are the collector and emitter. (lets assume an NPN)

I put the neg lead on what I believe is the emitter and the + lead on the collector.

Now the fun part, touch the tip of your tongue between the +collector(?) and base.

One of 2 things happen:
You either feel a slight tingle and not much lowering of the voltage, or you feel almost nothing and get quite a low voltage reading (C&E are correctly identified).

If the former reverse the + & - leads and use the tongue trick between the + and base again and it should result in C&E are now correctly identified.

I can run the tongue test in a few seconds and it has never let me down - but the new part tester gives me the pinout, VBE, actual gain figure, npn/npn, and feels a tad more professional.......
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
     Page 3 of 3    
Print this page


To reply to this topic, you need to log in.

© JAQ Software 2021