5v source on Kunteng controller

Pegazus

100 mW
Joined
May 18, 2019
Messages
45
Hi,

I'm looking for a 5V source in a kunteng controller to power an arduino pro micro.

What is the best place which can provide amp : throttle, PAS , something else ?
 
first, how much current does your arduino need? the 5v within a controlelr is typically only able to supply a few dozen ma at most, and that includes powering it's own mcu, throttle, internal transistors/chips/etc., hall sensors, and so on.

so there's not usually much leftover after that.

you can, of course, change the 5v regulator out for one capble of higher currents, but htis will then need a higther current source so you then also have to hcange out the 12v (or whatever voltage) regulator that converts the battery voltage down for the 5v regulator input as well.

it'd be simpler to just get a small battery-voltage-to-5vdc dc-dc converter just to power your arduino. there's a lot of stuff that does that and it's usually really cheap.


so, if you only need a few ma to power the arduino, maximum, you can simply add a wire pair to the 5v and ground on your throttle, or hall sensors, or pas sensor, etc., without even opening the controller itself, and run those to your arduino.

but if it draws too much current it will drop the voltage on the 5v line too far, and the controller will operate unpredictably if at all. worst case it will damage the 5v regulator and cause the controller to no longer power on.
 
Just to put a finer point on the controller regulator. Many use a 78L05 voltage regulator, which as seen here puts out up to 100mA.

https://components101.com/78l05-pinout-equivalent-datasheet


Data point: throttle uses about 6.5 mA for a hall sensor throttle.
That said, I still like the idea of a separate power supply! (why take a chance on toasting your controller?) :roll:


Regards,
T.C.
 
if you only need 25ma absolute max, it's possible it would work.

if you prefer to verify this, you can cut the trace from the 5v regulator system output to the rest of the contgrolller, and insert a good multimeter or ammeter in series with that connection, to verify the amount of current the whole existing system takes without your arduino setup.

then look up the spec for the 5v regulator that's actually on your controller board, if it is one of the single-chip types like the one posted above.

if it's a section of the board built into a switching regulator smps, then you have a harder job, looking up the specs for teh siwtching transistor and guesstimating how they actually use the parts to get a guesstimate spec for max current.


once you know that, then you can subtract the existing system's load from teh capability, and then see if there's enough left over to run your stuff. if ther'es lots of clearance, you're proably ok. if it's really close, it might work fine or there may be transient loads you don't know about that go over the limit and either sag 5v down too far or end up damaging the regulator. depends on system tolerance.s
 
Also keep in mind that it is can be handy to have a nice, robust, 1-2 amp 5v power supply on your ebike to charge your phone and/or certain battery powered accessories such as lights. So the small investment (less than $20) might have benefits beyond your immediate need/concern.
 
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