Put adjustable current limit on my speed controller

Lowell

100 kW
Joined
Jan 12, 2007
Messages
1,695
Location
Vancouver
A big thanks to Fechter for posting the info, and it works like a charm. On zero, current goes down to about 20 amps, and it's easy to dial in your setting to within a couple of amps.

This would be a really cool mod combined with a slide or thumb control on the left bar, or perhaps several click stops like indexed shifting.
 
Thanks for the report. I think you're the first one to try it.
You're promoted to Crash Test Dummy. :D

The way it works, if you install a 3 pin connector on the controller and have a remote knob, the limiter would go back to normal if you unplugged the knob.

Any idea where to get those type of connectors they use for the throttle and brakes?

Just have to figure out a nice way to mount a knob on the handlebars. A rain-resistant one would be nice.
 
Could you do a complete tutorial so that what you've learned can be shared by all?

Also, is there an easy way to switch to motor side current limiting? I want constant torque at the rear hub (and less heat) so this type of modification would do wonders to make things better.
 
aye Lowell/Fetchie..I'd like to try this...what do I need to buy, and to where should it connect? (handy with a soldering iron, but could do with pics as well as schematic :roll: ) Thanks Muchly!
 
It's burried somewhere in here:
http://endless-sphere.com/forums/viewtopic.php?t=764

about half way down on page one.
 
I scoured through last night Fechter, but couldn't see exactly what kind of pot I need to find. Am I right in thinking that if I just add the pot at the end of the bridging wire i've used, it will let me adjust from the original 20A up to the new 30A? Does the pot take any load? (does it need to be beefy?)
 
I guess you have the small controller, so the layout is a bit different.
Let me know if yours doesn't look like the one below.

You need a 10k pot and two fixed resistors. In the schematic, if you replace the 51K pot with a 47K instead, you can increase the current limit. I'm not sure exactly how high it will go with 47k, but decreasing the value of that resistor increased the maximum current.
The pot and the resistors have very low current, so they can be tiny ones.

In the photo, the connection points are indicated. I just used very thin wire to attach directly to the legs on the chip. I soldered the fixed resistors directly to the pot, and ran wires from there. The resistors need to be braced so that they don't vibrate and break off later.

The pot can be mounted through a hole in the end cover, or you could extend the wires as long as desired to make the control knob easier to reach.
 

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  • 20A controller Current Adj.jpg
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if you replace the 51K pot with a 47K instead
Isn't this suppose to be a fixed resistor?
 
Cheers Rich

Do you need to add a bar to the busbar as well if you want to increase the current? to make it up to 30A? I will do this mod on the little controller that DC is going to run on his Puma, he can then take it up slowly until he finds a nice happy limit.

Thanks for the info, its nice and easy to do, I can test it easily as well using my watts up meter or data logger.

Thanks

Knoxie
 
You can do it both ways.

By lowering the 51k resistor, it will increase the limit without touching the shunt. The downside is the stock shunt has to take the full current. I think it will take 30 as is without overheating.

The other way is to solder the shunt to lower it's resistance. If you do that, then the 51k should stay and you can only lower the limit with the pot.

Soldering the shunt is not very precise, so it's hard to know what the limit will be afterwards.

It would be nice to know what it does with a 47k, since this would be fairly consistent.
 
Hi Richard

Yes thanks again I will surely let you know, a great little mod easy to install as well, I have all the bits at work so will hack it in to the case tomorrow dinner time! will let you know how it performs!

Knoxie
 
Excellent Fechter! I'll get some supplies in and solder them in. Since I already have the shunt fixed up to 30, i'll only need to decrease current..

I'll report back when done..

Love you forever...

Jozzer
 
Hi

Well i got around to modifying the 20A controller, fitted the pot and resistors, I used a 47K so will report back what the watts up meter says, I have strapped it to the other bike and will take it out tomorrow night after work and do some tests, should be really easy to see if it works or not. I used the battery back up on the watts up, strapping a 9V to it holds it high so even if the BMS cuts it doesnt loose its memory.

Makes the bike look like its running off a 9V! ha ha

Cheers

Knoxie
 
Excellent, worked a charm:) Current now adjustable from 5 amps to 30.
Range took a dive when I modded up to 30A...now I can turn down when I need to go further :D
Thanks for the Pro advice Fechter.
 
Perfect, thanks for the report. I wasn't sure what the max current would be with the 47k.

I love the chicken head knob. That's really old school.

If you installed a connector between the control pot and the controller, it will revert to the stock current limit when the pot was disconnected.
 
Ahh...i used a 50k, and left my original shunt mod intact. You'll have to wait for Knoxter to tell you what the 47k res does...
 
Hi

Well took it out on 37V and the current limiter works great minimum setting is 5A and the top one is 20A I couldn't get more than 20A, but thats ok for now, so the 47K resistor doesnt change it as much? it works great though and it really wont pull any more current than what you dial In, i tried it climbing up a hill and it was perfect, a great way of locking the amp draw and nice having the adjustment on the bars, a must for all of the controllers and more usable than the DB feature as that looks tricky to change on the fly.

Thanks again Richard for another top tip!! I will do this to all my controllers i reckon, need to actually go out and ride some of my bikes for a while now been so busy going to enjoy them for a while!!

Knoxie
 
Thanks Knoxie,

I guess it might be fun to try using 33k instead of 47k or 50k to see how much the current can be increased.
 
Hi Richard

Yes I will try that the next time i run it, going to enjoy some of these amazing rides I have now whilst the sun shines!! adjustable current limit is king though! nice one man :)

we happy

Knoxie
 
Hi all
This current limiter can it be used to control max speed or wattage, so the trike can be made to seem legal to the boys in blue.
Yesterday after I had done tests on the replacement motor I had fitted I tried some uk legal speed tests, I moved the throttle up untill I hit 15 mph (uk legal) after the readings had settled the meter read about 250 W and 5 A with a speed of 15 to 17 mph.

Wonder if there is a circut out there that can mesure frequency and at a predetermined level (alterable) send an output signel wire high. If we linked this to the current limiter then we could have a controlable top speed with all the aceleration of a high current system.

One more thing if I read this correctly then once the current level has been reached, any extra speed would require pedel input to lower the strain on the motor and so give the rider a workout on the cycle and still go at a fast speed, This would be like when the motor is going and you are not peddeling the ammeter might read 15 A if you start to pedel then the speed starts to go up and the strain on the motor goes down causing the amps to drop.
 
="geoff57"

Wonder if there is a circut out there that can mesure frequency and at a predetermined level (alterable) send an output signel wire high. If we linked this to the current limiter then we could have a controlable top speed with all the aceleration of a high current system.

One more thing if I read this correctly then once the current level has been reached, any extra speed would require pedel input to lower the strain on the motor and so give the rider a workout on the cycle and still go at a fast speed, This would be like when the motor is going and you are not peddeling the ammeter might read 15 A if you start to pedel then the speed starts to go up and the strain on the motor goes down causing the amps to drop.

That could be done. I think the new DB2 will have a feature like this.

The signal from a standard bike speedo (or from the motor hall sensors) could go to a frequency-to-voltage converter, then to a comparator that clamps the throttle. It would accelerate quickly to the setpoint, then stay there unless the load increased beyond the current limit (like a really steep hill), in which case it would slow down.

This could be done independently of the current limit adjustment.
 
Hi fechter
thanks I knew there must be a way, just couldn't work out how to do it.
I've read the specs on the db2 and I think thats where I got the idea from, but like Knoxie said this will be more easy to set on the fly than the db2 will be. but who knows untill they arrive, but for me, knoxie and others in the uk the db2 is going to be very hard to get hold of :( unless somone desides to inport them :!:
 
Justin mails out easily enough...at least he will when he has enough in stock! He likes us britishers. :D
In fact, it may well be that he will be the only one with DB compatible controllers for a while (just a guess...I know nothing!).
 
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