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Variable 5V to 12V voltage step-up. Ideas?

Started by MistyBlue, March 12, 2020, 03:55:26 pm

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MistyBlue

I have a 5V FDS IBL card that controls my pedestal panel lights using a dimmer pot plugged into the card.  But I also have 12V throttle quadrant lighting that I need to be able to control from the same 5V IBL card.  So I'm looking for a way to step up the variable 5v IBL card output to a variable 12v output to feed the TQ.

Thinking I should add a 5V to 12V step-up something like this:

https://www.amazon.com/Converter-DROK-Voltage-Regulator-Transformer/dp/B01L90B3RI/ref=sr_1_6?crid=WH04FZM7NAOJ&keywords=5v+to+12v+step+up&qid=1584056996&sprefix=5v+to+12%2Caps%2C181&sr=8-6

Does that make sense or is there a better way to do this?

ame

It looks like the FDS card has a 555 timer IC on it. Can you see the board and read the chip number? It's not legible on their website.

If so, it's probably using PWM to dim the lights. Therefore you could probably use the PWM signal to drive a buffer transistor or MOSFET and switch 12V instead of 5V.

ame

Ok, I'm convinced it's just a 555 doing variable PWM to control the lamp brightness (instead of some funky voltage control or current limiting).

Something like this ought to work:

https://www.aliexpress.com/item/32615078664.html

(search for opto-isolated MOSFET)

You should be able to connect one of the bulb outputs from the dimmer board to the control input of the MOSFET board. The optoisolator on the MOSFET will act just like an LED or bulb on a panel and will be switched on and off rapidly by the 555 on the dimmer board (the longer the 'on' time compared to the 'off' time, the brighter the bulbs appear).

The output of the optoisolator drives the MOSFET. You connect your 12V supply to the power input on the board and your 12V LEDs to the power output. The MOSFET will switch the 12V power off and on at the same rate as the 5V LEDs, and therefore control the brightness in the same way.

I can not recommend that specific board as I don't have one. There are several to choose from, and you might find one from a local retailer instead of waiting a couple of months to get one from China.

I have one of these driving a 24V 1A LED strip in my kitchen from a 3.3V PWM output.

https://www.aliexpress.com/item/32671829582.html

As you can see, the design is very similar. There's very little variance because the technique is so common.

You probably won't need a heatsink, but you could add one if you like.

MistyBlue

Hi Ame, thanks a ton for the very helpful response and sorry for the late reply (was having trouble with this site showing up as malicious for some reason).  Haven't gotten in to take a picture of the chip, but I'll look more into what you said and see if I can make it work.  It's a great start!

Very much appreciate the help!

Tony

ame

No worries. You don't have to take a photo. I found a manual with photos. It's a '555. You could take a look and confirm it for yourself.

I'm confident an opto-isolated MOSFET will work.



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