Greetings,

I’m a beginner with LED circuits so I’m hoping someone can help me.

I have a 9volt, 9 LED light that works great. The problem for me is that it has a LOW/HIGH/OFF switching circuit. I’d like to modify this so it only goes from HIGH to OFF.

Is there a jumper or mod to this existing circuit that could achieve this?

Thanks for your help.

lucem

 

There might be a resistor from high & low; if so short the resistor. Then there should be off-high-high.

 

I don't see the switch. What kind is it?

Can you sketch out the circuit.

It's probably pretty easy to do what you want, but the devil is in the details.

 

*Bernard - Thanks for the suggestion. I shorted R2 and got an overall light boost on both settings, but still low-high-off. Shorting the one marked 10R didn't do anything.

*WBahn - I believe the switch is irrelevant, I swapped it out with a standard on/off and still got low/high/off. I don't have a schematic, but I tried to trace out the circuit as best as possible... these things are quite tiny!

I found that the 6 pin IC is a 9920 High Power LED driver, but I'm not sure what the 8 pin IC is.

D1 is probably a diode.
I believe the 1210 and the 2302 are possibly varistors.
But I have no idea what the 15P and the 228 are.

Thanks for your help.

 

If you now have a switch that only has two positions, how are you getting three modes of operation?

How are you changing between the three modes? Sounds like the mode selection wasn't done by the switch in the first place, in which case the devil is even more in the details of how this particular circuit works.

My guess is that the 15P is a 15 pF capacitor and that the 228 is also a capacitor, but that would make it a 2.2 uF cap, which seems a lot for a chip capacitor that size, but they do make them.

 

I believe the 8 pin IC is doing some logic counting, switching amongst the 3 values - 0-1-2. Any idea how that can be modified?

 

I believe the 8 pin IC is doing some logic counting, switching amongst the 3 values - 0-1-2. Any idea how that can be modified?

It almost certainly cannot be modified. It is possibly a small MCU or a PLD of some flavor. If you can identify the functional pinout, then it may be possibly to replace it with your own part with your own programming in it. Normally that would be a daunting task, but the functionality of this circuit is likely so simple that it is doable.

 

Well…. looks like I figured it out. Perhaps not the best practice, but it works.

I went with the assumption that the 8 pin chip is an MCU - based on the 2 known pins 1=V+ and 8=GND, with Pin 3 (Output) to the LED driver. With a live 9v lead, I briefly touched Pin 2 (Serial In) to Pin 3, got a wisp of smoke and voila… no more LOW beam, just HIGH and OFF.

I’m curious to know how the professionals would have handled this.. perhaps just build it properly from the start instead of modifying an existing circuit.

Thanks again for the feedback!

 

Well to be honest, if I wanted to modify that device to just do off and high, I would have bypassed the circuitry altogether and controlled the LEDs with resistor/s or a CC device of my own design.

I had considered offering this suggestion, but I couldn't make out how the LEDs were wired.

 

...LEDs, 555s, Flashers, and Light Chasers