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 Help with circuit for flashlight and enabling mode
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Starting Member

2 Posts

Posted - 04/12/2018 :  01:55:38 AM  Show Profile  Reply with Quote
I am having an issue with a circuit I would like to try. Its for a flashlight and enabling modes.

So I have the buck step down driver which uses the IC ax2002, here, and the datesheet
I would like to cut the enable pin which takes a positive input and somehow use a switched negative output from a 3 mode driver.

So the EN pin on the ax2002 is connected to the + with a 10k resistor. The board I have for the modes modulates the - side. I need to somehow turn the - into a positive.
Now I was thinking of a transistor, but iím not sure what part is available (if any) to take a neg- input and send out a positive output to control the enable pin on the second board.
Also, the EN pin input is sensitive enough that even touching it and a + lead will start the IC.

I donít have a circuit yet as I donít know what part would be suitable. I need to take a negative 12v modulation signal and convert it to a positive to drive pin #2 (enable). The boards are china made and I donít know
what the chip is on the 2nd 3-mode PCB as the info is sanded off.

The board on the left is a boost driver and has nothing to do with this. The leads going to the
smaller board is white neg- side to the modulation input. The red pos+ is needed but just passes through
the board. The white and red leaving the small PCB is the output and the silver thing is an LED. This smaller board just modulates and doesnt control current or voltage.

So the idea is to tie the output of the small PCB into the EN pin of the 2nd larger board below. The input for this PCB is on the underside of the PCB and rated 3.6V ~ 18vdc. The small black and red lead on the top of that board is the regulated outputs for a high current LED.
So what im trying to do is change nothing aside from cutting the enable pin from the pos+ and interrupt it with the modulated signal.

Regarding the 10k resistor, that would still be needed between the new modulated + source and the EN pin. So same config, just interrupted with the modulated signal...
By the way, The power supply is 3 li-ion cells in series so 12.75vdc at highest. Im thinking a few diodes to lower the voltage into the 3mode board on the neg- side. The 3mode board runs on the output of a boost driver meant to run between 5-9v so I have to test and see what the upper limit is.

please bare with me, i'm still green at electronics so i'm learning as I go.

Thanks guys,

dave w
Average Member

60 Posts

Posted - 04/12/2018 :  3:22:07 PM  Show Profile  Reply with Quote
Hi Elijah! This is the SmartHome forum. SmartHome markets home automation goodies. So this forum is manly for HA users. Seems like your question would have a better chance of getting answered on Candle Power forums which is a LED, LED flashlight, batteries, chargers, etc. forum. BTW I think I would use a fixed regulator like a 5V, or 8V 7800 series rather than stacking diodes. A diode will drop about 0.7 V so you will have a wad of 6 or so diodes.

This aftershave makes me look fat.

Edited by - dave w on 04/12/2018 4:51:11 PM
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Starting Member

2 Posts

Posted - 04/12/2018 :  7:47:10 PM  Show Profile  Reply with Quote
Hi friend, sorry and thanks, your speedy suggestion is a good one and i will give a try, very appreciate, if things don't go better, maybe i will find another more proper forum to ask my question again, have a nice day!

Edited by - Elijah_C on 04/12/2018 8:10:45 PM
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Starting Member

5 Posts

Posted - 01/03/2021 :  05:44:48 AM  Show Profile  Reply with Quote
Bro, if you don't want to break your flashlight just don't use it anymore. Seriously, you could not have anything with such an attitude because technical things are easy to break now. I don't think that you're unlucky though. I had several flashlights which eventually stop working but that wasn't my fault. The fact is when I finally bought a good model I understood that the problem was not in me. You should check out the Vont 'Blaze' Tactical Flashlight for yourself.

Edited by - MattRandalloK6 on 01/05/2021 07:57:15 AM
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