Soft-latch switch single button ON/OFF & reset for Vedder anti spark : BOM?

EDIT² : I updated the BOM at bottom of this post.

The title says it all guys :smile: Btw I realize this is my first thread ! It’s time I started moving my lazy ass.

I need a reliable yet very flat & compact switch button for my skates so most mechanical buttons can’t work for me. I simply don’t have the space for the cylindrical body and toggle switch is out of question ! And I’d like to make a custom button shape and material with RGB LED for a sexy finish. Momentary push-type is sleek.

I already got a vedder-type anti-spark module from @goldenHusky, what I only miss is really the switch itself to command the module.

So… I’ve been itching to build a soft-latching single button switch instead. If you look around, you’ll find tutorials with different methods to achieve that - first example :

Please note that this example have the drawback of starting in “ON” position and not “OFF” yet we do want the switch to always start disconnected. So we’d need an auto-reset function included to guarantee that.

Edit : we also want a delay function (push ON / hold 2-3seconds OFF) !

Well there are good news : @s28400 has done the hard work to make an auto-reset soft-latching switch interface with Vedder’s anti-spark module ! There is no update on the matter since September 2016 and no BOM posted but as shown below it was already working back then with all wanted features :

Posted from his page “radical-creation” :

The best solution I have found is a soft latching switch circuit. This utilizes a momentary switch to latch a logic signal high or low. A slightly modified version of this circuit will yield a push on and hold off configuration. This is ideal because it is the most reliable and most robust of all the options.

I put together a quick circuit on a breadboard and interfaced it with a mosfet. I will post a full schematic once I finish it. Anyway here is a video of the working circuit.

It seems to work perfectly and I will next look to reduce the size of the circuit by making it on perforated board and possibly a custom pcb.

So what we lack is a PCB with a BOM. Can you help me source proper parts to try this out ? We can make a great low-profile custom switch to plug on our anti-park modules thanks to Joshua’s work.

Here is the schematic :

Proposed BOM (work in progress) :

  • 1x Linear regulator : LM317HVT (60v max input, programmable output to 5v - need a pair of resistors or potentiometer to fix 5v output - good up to 12s/13s) or 1x LM7805 linear regulator (40V max input, fixed 5v output - no resistor needed - good up to 8S)
  • 2x 100kOhm resistors
  • 1x 5mOhm resistor
  • 2x 1uF capacitor (from the bucket)
  • 1x 1mOhm resistor
  • 1x heatsink for the regulator
  • 1x NAND gate (5v) - I went for CD4011 chips, cheap 4x NAND available on eBay
  • 1x MT3608 boost converter or 1x LM2596S step-up converter for excitation of “C” pin
  • 1x 12v zener diode
  • 1x irf510 mosfet
  • 1x momentary push button (you can either get a mechanical one or recycle one from a TV remote)

Optional (for some custom) :

  • 1x simple LED or the combo
  • 1x ws2812/sk6812 RGB LED or more
  • 1x arduino (Nano or else)
  • 1x 470ohm resistor
  • 1x 1000uF capacitor

Next step (work incoming) :

  • The wiring !

u will need pretty sick voltage regulator if u have 10S :smiley:

I’m not sure because the switch itself may not see as much voltage!

U connect ur 5V regulator to + of battery

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“Push On / Hold Off” would also be way safer, if a stick or debris bumped your switch, your board would not shut down. Or heavy vibrations would not shut your board down either… me like

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How are the mechanical push-lock or toggle switch usually plugged to the anti-spark ? I was thinking we could feed power to the soft-latch from same source at least to limit current. Then we could look for a big regulator as you pointed out (thanks btw!).

a 60v regulator would give some margin… but maybe selecting different modules for lower voltage would allow less wasted heat on the regulator ?

Edit : sorry I misread your post. Yea, push ON / Hold OFF !

If boosted can do it so can this community :grinning:


I actually traced down all my “Evolve remote disconnects” to a problem where the (mechanically-latched) power switch disconnects for a few milliseconds under vibration and shuts the board down…

So improvements like this “hold for off” soft power button can actually have really important safety implications under the right conditions

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@b264 that’s pretty scary. All the more a reason to sort this circuit out.

I narrowed a first choice for the regulator : LM317HVT chip in TO-220 package !

Pretty cheap and seems reliable. Would need a heatsink to manage heat. It has programmable voltage though, how do we manage that ?

You can do that by selecting the values for the resistor R2 or using a potentiometer. What voltage do you need?

Ideally I need 5v fixed output voltage from the regulator.

Edit : what about the NAND gate, is this one a good choice ?

If you need 750mA or less (3.75 watts) use an LM7805 instead of the LM317HVT

I got some spare LM7805 in hand but I think max voltage input is 40v ? It would be good for max 8S (which is enough for my build though) no?

Oh, good point

What about this, it’s smaller and cheaper

Plus you get to demonstrate your soldering prowess ha ha ha

Haha well my soldering skills are at lvl 5 - trainee but I fear not ! Though I realize that I got a handful of these in a box

So I’ll experiment with these ! And it is cheap too (and bit bigger pins so hopefully I won’t fry them while soldering) !

Edit : Ok we’re almost complete for the BOM ! What’s left is a MOSFET and a momentary button (but I’ll salvage the inner button from a TV remote I think). Maybe we need a boost converter for excitation of the “C” pin ?

I received 2x MT3608 modules which could do the job, still very compact and flat modules. Just plug it after the MOSFET and voilà !

Actually the LM2596S are a great part for this but they are $5 each (10S max)

Ok I added it to the BOM. I just ordered irf510 mosfets to complete the circuit, pretty cheap too!

It’d be awesome if we could find something just like LM2596S except that works on 14S … also the DC-DC converters already built are cheaper than the chip itself