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Help Debug Circuit

ThomsCircuit

Active Member
For clarity Ive done the best i can with the schematic program to place the vetris peak detector in this diagram. im using a relay K1 to simulate the device.
I made this in the past on a prototype board. And while the bread board mock up worked the PCB did not. I put it aside for a few weeks then came here for help. As I set up to start debugging the board it started working. I could not understand why but accepted it and built a second one. It did the same thing then started working after i let it be for a few days. Its been a year and both of them still work. they are in my shop and work fine. I decided to make 5 more. this time i had pcbs made, changed the relay to a smaller one and used different pots (vr1 & 2) As i soldered each one i tested them. they worked. I was very pleased. I set them aside for a few months while i worked on another project. Now im ready to box these up and start using them in my shop. Ive got new peak detectors so i set up for another test. Wouldn't you know it they dont work. Ive tested two boards and they do not work. Can you guys help me figure out what may be wrong here? Why this circuit is so flaky? I get power. The peak detector triggers fine, which then closes the switch on this circuit but the signal switching relay will not close. Help me test this so i can get to the bottom of this.
12V power supply
Work Shop Delay REV2.1.jpg

WSD pcb.png
 

AnalogKid

Well-Known Member
Most Helpful Member
Lotsa words, no useful information.

What is the device?
What is the circuit?
What is it supposed to do?
What is its intended operation?
How is it supposed to function?
What is the function of Q2?
What supplies base current to Q3?

AND - What does "don't work" mean?

ak
 

ThomsCircuit

Active Member
1What is the device?
2What is the circuit?
3What is it supposed to do?
4What is its intended operation?
5How is it supposed to function?
6What is the function of Q2?
7What supplies base current to Q3?

8AND - What does "don't work" mean?
1 A current sensor
2 I do not understand how to answer this. The circuit is the schematic i provided in post #1
3 The "device" closes the the circuit. after a delay of 1-5 seconds the switching relay is supposed to close. That part does not happen.
4 As i described in the above line 3. I use this in my work shop to turn on a vacuum. it is triggered by this circuit after i turn on the table saw.
5 As I described in line 3 & 4
6 I do not know. I had help from this group making this.
7 This is how it was designed. My knowledge of transistors is limited.
8 the signal switching relay will not close. It is on a delay controlled by VR1, R1, & C1
 

danadak

Active Member
Might help if you build a table of voltages at certain points before
and after delays. Key would be transistor EBC voltages. Signal relay
not operating implies Q1 not turning on.

Start with that, its tedious getting the measurements, but a DSO with
qualified trigger and datalogging the key voltages in a graph (many
DSOs have this) will show you what node V's are doing. Or a voltmeter,
here if delays short parallel big cap(s) with delay cap values to slow down
delays so you can get V at beginning of delay.

Regards, Dana.
 

ThomsCircuit

Active Member
Ok so I understood some of that.
Table of voltages. I can measure EB & C of Q1 2 & 3

The rest is not something I understand.
What is a DSO with a qualified trigger? and what is a node V

I can follow directions as long as I understand what they mean. A lot of this i just don't understand. I put this together with help from this group. I know what transistors are but why they are connected this way I don't know. I know they amplify. I know what a resistor is but I do not know why they are connected the way they are in this circuit. I could only configure which resistor to use to power an led. Just trying to give you an idea of what I know. I have made many things here. They all work. This ones behavior however is bizarre. It works on bread board but not when I put it on the pcb. Im asking for a bit more guidance. Please.
 

AnalogKid

Well-Known Member
Most Helpful Member
6 I do not know. I had help from this group making this.
I sorta kinda remember other threads about a shop vac. Please post link(s). The schematic has errors that I think the group would have caught, but I can't tell without the originals.

ak
 
Last edited:

ThomsCircuit

Active Member
Ive got a image of the back of the pcb with some key points to test. If this helps you guide me i can test points. The fella who helped me build this is no longer here. He was going to guide me in finding the fault in this circuit.

this is the link to the page for this circuit (Auto ON-OFF)

20211126_233940.jpg
 

ThomsCircuit

Active Member
Also, what are the functions of each of the four circles devices on the right?
LOL that is my attempt to create an outlet. the top right one being a switch.
one for the saw, one for the vac, one to power the circuit, and an over ride switch so i can turn the vac on manually

Electrical_Receptacles454-DJFss.jpg
 

ThomsCircuit

Active Member
The Halkeye 300 is meant to replace his makeshift current detector. He updated his schematic but neglected to remove the transformer and its components
F1 T1 C1 D1 D2
 

danadak

Active Member
Ok so I understood some of that.
Table of voltages. I can measure EB & C of Q1 2 & 3

The rest is not something I understand.
What is a DSO with a qualified trigger? and what is a node V

I can follow directions as long as I understand what they mean. A lot of this i just don't understand. I put this together with help from this group. I know what transistors are but why they are connected this way I don't know. I know they amplify. I know what a resistor is but I do not know why they are connected the way they are in this circuit. I could only configure which resistor to use to power an led. Just trying to give you an idea of what I know. I have made many things here. They all work. This ones behavior however is bizarre. It works on bread board but not when I put it on the pcb. Im asking for a bit more guidance. Please.


DSO is a digital sampling oscilloscope. When you use a scope its trace on screen is
started (triggered) by an event, like when a V is reached, or a rising or falling edge
of a pulse or a logical value (example state of pins)....

Look at the second video first for further interest - https://www.rigolna.com/basics-of-oscilloscopes/

Node V is a point in circuit where you measure voltage. The junction of a resistor and
another component is a node, Where ever two or more components or sources, like
V or I meet.

Here is example of a circuit where all the nodes are labeled (in this case with numbers)-

iu


Regards, Dana.
 
Last edited:

rjenkinsgb

Well-Known Member
Most Helpful Member
so From pad 2 of R1 to the base pin of Q3 with a 47k? ok ill do this in the morning.

Sorry, I meant purely as a diagnostic test to see if the rest of the circuit then functions reliably, not a permanent change.

If that works, then probably a 5.1V or 6.2V zener diode as a more consistent alternative to the reverse transistor junction.
 

ThomsCircuit

Active Member
I did the mod and the board worked. However while the delay stop is adjustable the delay start is not. I can only get ½ -1 second delay. Its acceptable but I think this project could be better. Perhaps with 555 timers.

Now I re-connected an unmodified board that did not work yesterday and it functioned today. Not perfectly but while the led that shows that the switch has been tripped its delay on and off worked with a start delay of 1-7 seconds and stop of 6-20 seconds. I tested a third and it did not function. The delays that is. Bizarre to say the least. Do you fellas have any feedback on why this is? Why the resistor swap makes it more stable?
20211127_095414.jpg
 

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