5k pot alone as throttle?

[yoyoman]

Considering that this is my "last mile" bike, is there any reason I couldn't be cheap about it and just use a 5k pot alone as my throttle?

That being said, can I just pick up the cheapest 5k ohm potentiometer at Radio Shack, and perhaps add a wide knob to the pot shaft?

 

[yoyoman]

hmm, probably a little dangerous if the pot accidentally turned, which is likely the purpose behind a spring keeping the pot dialed down. Maybe will skip the knob and mount it in a small box or something to prevent accidental throttling.

 

[d8veh]

It'll work OK. I used one as a cruise control with a switch on the signal wire to switch it on/off. Make sure that you have brake cut-offs, which you can use to control the bike: Pull the brake to stop the motor; let go to go.

The adjustment is not very precise. If I made another one, I'd try a 1K resistor on the signal wire. It should give a better response and it will also give a bit of protection to the controller.

 

[Matt Gruber]

i'm hooking up a "motor speed control" which comes with a 100k pot and a 1/2" knob. the small knob works great in testing.
for safety i'm using a momentary on push button on the left hand. it hooks to 80a truck relay with silver contacts. if my thumb comes off, power is cut. no need to grab brake to cut power. i also use the minimum amp fuse.

 

[yoyoman]

excellent suggestions. The switch idea came to mind earlier, but using a momentary switch is much smarter!

Thanks! I've let this bike languish away as a regular bike for too long =) I'll fix it up tomorrow and forget about trying to salvage the bad pots.

 

[Matt Gruber]

there is a bit more to my wiring.
i use a 220 ohm 3 watt resistor across the relay to keep the caps charged so there won't be a BIG spark.
But i don't ride everyday so this will drain the pack slowly, so i
use a ON/OFF switch hooked to the 220 ohm. WITH an LED/3k resistor on the handlebar, where i can't miss it. Anyone without an easy to see LED will, sooner or later, leave the pack on by mistake, and ruin the battery!
.
as your controller has a built in kill circuit hooked to the brake, you can, instead of buying a relay, hook a momentary push button to the brake switch wires, in parallel and the brake kill will still work. It may need a normally closed push button, the opposite of mine.
Anyone that hates their twist throttle should convert to this system and see if they like it better. with a knob, u can mark your favorite spot, and get it right every time, and not get a tired hand, and have instant kill when you release your left thumb.

 

[motomoto]

I used to use an astroflight servo tester as a throttle and would turn it all the way up and bang thru the derailleur gears until I had to switch it off and hit the brakes to not slam into the building. Not smart in my case.

 

[yoyoman]

so, Radio Shack didn't have any 5k pots, so I bought a 10k one. I also bought one that had a built in switch, like an audio knob.

It sounded funny the first time I turned it on, so I turned it off fairly quickly. The next time i turned it on, it looks like the master link of the small chain of the USPD sprocket' broke, and it sucked the chain into the planetary gear housing. I left it there for now.

I removed the motor from the bike, and I plugged everything in again. Now, I get nothing when turn the pot. Is there a chance that the controller burned out or something due to the motor not being able to turn when the chain was getting sucked into the housing?

I tested the pot with my multimeter, and everything seems to be normal. The NiMh battery is right around 25v, but it was low when I started.

 

[Matt Gruber]

good chance it blew a fuse when it ate the chain.

 

[yoyoman]

Well, the bike has a USPD motor with integrated controller, and I don't see how the can opens up, so I am going to let that one sit as dead for now. I have a BMC can motor, also with integrated controller, that I removed from an old Currie e-ride bike, and with my switch+throttle it sounds pretty smooth. Now I'll have to extricate the chain from planetary gear housing or steal it from the e-ride. Gotta love $40 parts bikes!

 

[yoyoman]

Today is the first time to ride with my new/used BMC 800W motor which replaced a Currie USPD motor. I also am using my hackish looking 10k pot.

The ride was very sluggish compared to what I remember. Would the 10k pot be the culprit since the stock throttle is a 5k pot?

 

[d8veh]

The ride was very sluggish compared to what I remember. Would the 10k pot be the culprit since the stock throttle is a 5k pot?

Not if it gives out 4v at max.

 

[yoyoman]

My nimh pack is at 27v now. I'll try again tomorrow. Normally I charge at work after my short 2 mile ride, but I didn't yesterday, and it was a low 24.3V when I got home. I don't recall it ever getting that low before with the old motor and throttle.