Switching higher voltage dc for lights

Ok so i need some help and advice on a project. My goal is to setup integrated lights on my new build as well as replace some of the analog solutions I’ve used previously but my experience level with solid state switches is super meh. The more analog systems im familiar with either don’t work because of the difficulty breaking even low current high voltage dc. I.e. 80-100v dc relays are expensive and fail in ways i don’t like or are way too big.

My first thought was to use a transistor for switching (tip122 and tip122) but in experimenting with it i ran into two issues. The first was that I missed on the spec sheet that I would need 100ish milliamps to switch it on and if i want to have multiple parallel circuits it would quickly add up to a lot of heat and could quickly overload the 5v output of most vesc. Second is a failure could damage the esc by putting high voltage on the 5v of the esc. Isolating it seems like an absolute requirement and really should be a part of any solution. Last thing i want to do is kill a vesc because i want tail lights lol

I keep looking around for some off the shelf solution but im split wanting to make something and learn a bit more about this stuff and also there doesn’t seem to be anything available I could copy.

I want to be able to switch my lights on when the board is turned on, as well as chose which sets of lights will be running. More to come here but i just wanted to start the topic

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@ShutterShock came up with the idea of running the lights of the LLT BMS discharge port (or maybe accessory port?). You can turn that on or off with the Xiaoxiang BMS app. If you have a smart BMS (JBD/LLT) this is a good approach

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@DuckBatterySystems has something that’ll switch HV with a 5v signal (momentary, not latching)


This does indeed work well EXCEPT unless you also have a physical switch, the lights turn on when you have the board on the charge. Kinda annoying.


So i tried this and found it lacking. It didn’t respond and was clunky. Often it would not disconnect power at all or would fail to change state. Im not sure if it was an app related issue but it also runs independently of the vesc and is kinda always on/off if it does get stuck.

With my other 12s build it just refused to work, on this 18s build there is no output on the bms at all so not an option to test unfortunately.

It’s still Alpha testing as far as i am aware, it looks interesting but i don’t even see a build thread or hints about it besides vague references to it and the web store listing. What i want to do (hopefully) will be much more basic.

I want high voltage in, switched output. Control via 5v from vesc series with a physical switch - with basic isolation of the 5v control from the vesc from the switched voltage. Im going to throw my head at it again tonight and see what mess i can make with the junk I have lying around.

End goal is to have a basic simple module - it’s obviously not easy but it should be doable right? There isn’t any reason it hasn’t been done before except that it seem like not many people care about it. I just hate all the fiddling and charging required to use battery lights.

Long term after i get the switching sorted i want to try and grab a break light signal from the vesc also but that is definitely step 8-9 in this process.

Maybe i just need to work on an isolated 5v hand off circuit first? Seems like a good place as any

That’s exactly what the DBS Accessory Smart Switch is. Like, exactly.

Yes and no. It’s not listed for sale yet, mostly because I’ve been too busy with other shit. However it’s also in every Hoyt and Metroboard that has been shipping for the past year. So :man_shrugging:

What is the max load you want to run through your switch? What voltage?


18s 75.6v is the battery voltage i want to switch, max single load is like 1.6a (i think this is after the buck to 12v) max on a single circuit so very low load.

It should work at up to 20s

Just found this amazing item on AliExpress. Check it out! $24.00 | Factory customized voltage 75~150V to 5V/12V/24V Isolated DC DC Converter

I’m curious about the thing from spintend too. Still need to reduce voltage to 12v though, so not what the op is looking for. But I’d like to figure out if using a spintend remote and receiver connected to it could potentially make it work with any vesc.

They say can work with any Vesc. I got one I plan to hook up to a bike to make it street legal…but waiting till the cops give me a warning, hopefully. But does brake lights which the op was looking into and hard to find. Only place I could find it

The step-down I posted is pretty big but either that vendor or another on aliexpress has smaller

I looked at the unit from spintend and just couldn’t justify buying another unknown from them, the 12v lights and break splitting units are super cheese at premium price

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Look at the buck offered by the zmote guy, 3a and 100vdc max. I have an old potted style consumer one but it is huge so i plan to grab one from him when i grab another zmote after testing


That’s tiny. But I fear I’ll maybe have high beams on, put on the brakes, and honk all at once or something and end up snapping …on a highway. Also doing 120v

But the dc thing I linked seems the only option for brake lights if using adc controls.


Ok big ask here: my free trial ran out on the circuit design and testing account so i hand drew the circuit:

This is mostly a combination of example circuits i found online and my very very basic knowledge of circuit design.

so I grabbed an optocoupler and using the example circuit it THINK it will only draw 10ma from the ESC 5v but I am not confident I understand the spec sheet and could be way off: https://www.vishay.com/docs/83503/tcet1100.pdf

Then to drive the 5v of the switching circuit I grabbed a 50ma linear regulator (ZXTR2005 https://www.diodes.com/assets/Datasheets/ZXTR2005K.pdf) and slapped that in there to drive the transistor (2n4401 https://www.onsemi.com/pdf/datasheet/2n4401-d.pdf) that turns on the mosfet (IRF9540NPbF https://www.infineon.com/dgdl/Infineon-IRF9540N-DataSheet-v01_01-EN.pdf?fileId=5546d462533600a401535611cfa21dc8)

bingo bango and bobs your uncle… I did not develop the passive device values and have literally cut and pasted them from example circuits from the spec sheets and tutorials like they are electronic Legos. This is how you make fire lol.

Any suggestions for a better way to cad and simulate the circuit before I just build a bom and order the parts to bread board it? suggestions and edits or is it just too chicken scratch to bother until i get it drawn up properly?

Kicad seems to be a hundred floors above me in the tower of design lol. Why do i feel like i live at the bottom of the learning curve?

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Kicad isn’t too bad once you figure out what the fuck is going on. That stuff I’ve been making for my nerf projects is all kicad. I’m not all that good at it, but I’m happy to try helping you out too. It’ll be a learning experience for both of us.


If you’re after a electronic solution, that’s totally fair. But I think it bears mentioning that the old school solution still works, the same way that we can switch the board itself on and off.

The running lights on my Orbital build were made by putting LED chips in series until they ran at 20s, then wiring them into the battery with an automotive blade fuse and an xt60 or xt30 loop key on the hot side.

It’s 18 degrees outside so im bored. I already have them installed and running in the conventional way you described (though my fuse is too big and is just for short circuits). When I can’t ride, i tinker.

im still waiting on the vesc to ship (ordered in may long story, i dont wanna talk about it) so I can clean up the wire management. waiting on the graphics so i can work on skinning it, and my work area is frozen so i couldn’t work with urethane or epoxy anyway. Finished my riser design, printed and installed. Battery has been done since October. One light is waiting to ship - because it was doa but otherwise it’s already wired up with full voltage rail and 12v rail.

Its literally the last thing i have left to make progress on until other people follow through or shipping ships the shippables.

I think it would be a nice little touch but it does work now without it. I also really like when i get something like this working well - if i can pull it off it will be absolutely forgettable. No one
Will ever notice it or comment probably but that’s also partly because it will just melt into the background. It’s kinda obvious that it should just work that way.

It will also lead to the next project which is to scrape a break signal out of the vesc or receiver some how which will likely be 3.3v or 5v and need do the same thing then anyway.

id love to buy one from dbs but the offer wasn’t made after i laid my specs out so maybe it wont work here or he’s just too busy, its all good i think i’m on the right track ¯_(ツ)_/¯ wont ever be as nice as an icb version but im only making 1 or three of them