Modify circuit

[Dietmar]

I am still struggling with the 12V unit which is used to connect four lights for a strobe effect.
Point no A is the on/off switch.
B, C and D is the control button for a different strobe effects.
If you press A, the unit turns on, but only starts flashing when B, C or D is pressed.
This I want to modify, because the strobe unit won't be visible in the vehicle.
I also don't want to use button B and C.

Could someone please help me how to bypass switch D?


The lights must flash (with selection D) when the the unit gets powered on.

 

[Kabelsalat]

I'll recomend you to draw a chematic to get the overview of the circuit. You may need to rearrange the components on the drawing so it's easier to read.

Also bear in mind that the pictures doesn't reveal name of transistors or ic.

 

[Herschel Peeler]

I'll recomend you to draw a chematic to get the overview of the circuit. You may need to rearrange the components on the drawing so it's easier to read.

Also bear in mind that the pictures doesn't reveal name of transistors or ic.

So remove switches B, C and D, and jumper across where switch D was.

 

[Harald Kapp]

So remove switches B, C and D, and jumper across where switch D was.

Test first whether this will work. Some devices will accept a button press only after they have been turned on. Checking this is simple: Turn the unit off. Press button D, then turn the unit on while still holding button D pressed. If that works, then Herschel's suggestion is the way to go.
If this doesn't work, another solution is required. Maybe a reset controller as used for CPUs may be (ab)used. You'd have to reconstruct the schematic diagram at least of the part where the buttons come into play by tracing the copper on the PCB between the relevant components. You're lucky: there aren't that many components.

 

[Dietmar]

I'll recomend you to draw a chematic to get the overview of the circuit. You may need to rearrange the components on the drawing so it's easier to read.

Also bear in mind that the pictures doesn't reveal name of transistors or ic.

Please don't critisize my drawing as I did my best to draw this.
I am also not sure if the transistors are drawn correct,
The switch I want to bypass is A, not the other one as mentioned before.
The IC does not have any numbers on.

 

[Harald Kapp]

The IC is probably a small microcontroller, programmed to blink as requested.
The transistors should have the emitter (arrow) to '-', collector (no arrow) to the lights.

Did you test the circuit as I suggested in post #ä4?

 

[Dietmar]

Test first whether this will work. Some devices will accept a button press only after they have been turned on. Checking this is simple: Turn the unit off. Press button D, then turn the unit on while still holding button D pressed. If that works, then Herschel's suggestion is the way to go.
If this doesn't work, another solution is required. Maybe a reset controller as used for CPUs may be (ab)used. You'd have to reconstruct the schematic diagram at least of the part where the buttons come into play by tracing the copper on the PCB between the relevant components. You're lucky: there aren't that many components.

Hi Harald
I have bridged the switch, but light does not come on when the power switch is pressed.
Switch only workes if power is on. Herschel's suggestion does not work.

 

[Harald Kapp]

Dietmar,
at a second look your diagram seems not to be correct. I'd think there should be a connection from the IC to '+' somewhere. But that may be totally unimportant.

You need to add a circuit that creates a delayed pulse after power on.
An exam ple is here http://home.cogeco.ca/~rpaisley4/LM555.html#29, section 'Power ON Delay Circuits', circuit #2. remove the relay, connect pin 3 of the 555 to the input pin of the chip on your board instead. Use any of the 555 calculators on the internet to create a delay of e.g. 10 ms ...100 ms, whatever is required for your board to work.

Alternative: use the 555 in astable mode to create the blinking without the chip on your board. It will only turn on and off, no fancy pattern.
If you want a fancy pattern, use a small microcontroller (PIC, AVR...) and create your own pattern in software.

 

[Dietmar]

I never thought electronics is so difficult. My apologies for dumb questions, as I'm trying to learn this field.
I want to keep my unit as the lights flash 8 times on either side. Also not sure what you mean by creating a delay?
When removing the relay as per diagram, is this the right way to connect it?

 

[Harald Kapp]

This looks good, give it a try.

 

[AnalogKid]

The schematic does not show the 5.1 V zener diode across the IC pins 1 and 8. This suggests there might be other schematic errors.

ak

 

[Dietmar]

The schematic does not show the 5.1 V zener diode across the IC pins 1 and 8. This suggests there might be other schematic errors.

ak

You are right! I have drawn a resistor instead of a diode.
Thanks

 

[davenn]

You are right! I have drawn a resistor instead of a diode.
Thanks

and the zener and pin 8 are shown as going to the 0V rail on the cct board but not in your diagram

how about redoing the cct diag a little more accurately

 

[Dietmar]

and the zener and pin 8 are shown as going to the 0V rail on the cct board but not in your diagram

how about redoing the cct diag a little more accurately

This is my first diagram I've drawn in my life. Don't know much about those things but try my best to DIY smaller things myself and thanks to Google.
How about some help?

 

[CDRIVE]

I never thought electronics is so difficult. <snip>

Huh?! The Earth must have stopped turning on its axis for this comment to go unnoticed.

Chris

 

[AnalogKid]

I never thought electronics is so difficult.

Well, now you know.

 

[Dietmar]

This looks good, give it a try.

Morning Harald
The link you send me for circuit 2..., what would the values of R1 and C1 be?
Thanks

 

[Harald Kapp]

what would the values of R1 and C1 be?

Use any of the 555 calculators on the internet to create a delay of e.g. 10 ms ...100 ms, whatever is required for your board to work.

 

[Dietmar]

I am stuck here. What would the delay time be for press of a button?
Is 100ms the right one to use? So R would be 10uf and C 15 ohms.
Am I on the right track here?

 

[Harald Kapp]

I can't tell you that as I don't know how the little chip on your board behaves. O'm afraid you'll have to test this. 100 ms is probably a good point to start.

So R would be 10uf and C 15 ohms.

Naah. R is in Ω, C is in (µ)F. And your values are way off. Using e.g. this calculator, I arrive at 1 µF, 100 kΩ (90.9 kΩ to be precise, but that doesn't matter in this application) for 100ms delay.
10 µF + 15 Ω result in ~165 µs.
Don't chose the capacitor too big. Read our resource on long duration timers for some more insight.