wiring up a pot/throttle

[atom1025]

Went to wire up my new throttle and the wire order is different then the old one.

From my controller I measure red as the positive. Black wire measures 5.1v. Green wire measures 4.8v.

Looking at the pot, wires facing me, knob strait up. (1) is orange wire (2) is brown wire (3) is red wire.

After a bunch of confusing and conflicting reads I decided I should wire red to red, brown to black, and orange to green.

Does this sound right?

What happens if you hook a pot up wrong? I want to avoid a full throttle surprise when I turn it on.

 

[ian.mich]

Went to wire up my new throttle and the wire order is different then the old one.

From my controller I measure red as the positive. Black wire measures 5.1v. Green wire measures 4.8v.

Looking at the pot, wires facing me, knob strait up. (1) is orange wire (2) is brown wire (3) is red wire.

After a bunch of confusing and conflicting reads I decided I should wire red to red, brown to black, and orange to green.

Does this sound right?

What happens if you hook a pot up wrong? I want to avoid a full throttle surprise when I turn it on.

make sure to do alll motor+controller testing off the ground with the wheel securely attached to the bike. I cannot say for sure what will happen when you do this, but i've encountered a similar colour mismatch and picking the closest colours usually works. you can always buy an ebike tester which can test throttles, and i imagine you'd be able to figure it out with that thing.

 

[atom1025]

I keep reading bout pots but nothing seems to pertain to my application. I have less of an idea now then before I researched.

Can someone link me to a page that will help me understand how these work?

 

[amberwolf]

If by pot you mean a resistive trhottle like the Magura, you could search on Magura and find a lot of posts discussing it (and a few about wiring).


But basically it is a resistor, from one of the wires to one of the others. Then there is a tap wire in the middle that allows the rotation of the throttle to change the resistance from taht wire to each of the others.

In most ebike use, it's being used as a variable voltage divider, putting a voltage across teh two main leads, and tapping off taht voltage on the middle wire.


To determine which wire is which, you use your meter on Ohms, usually in the 20K range.
1--Red lead on any wire, black lead on another.
2--Turn the throttle and see if reading changes.
3--If not, then you have foudn the two main wires.
4--Move red lead to the remaining wire.
5--Turn throttle and see if reading changes.
6--If reading goes up in value, then the black lead is on the Ground wire, and the red lead had been on the Positive wire, and is now on the Throttle Signal wire.
7--If it goes down, then black is on Positive and Red was on Ground.
8--If step 2 reading changes, then refer to step 6&7 for results.


wikied
http://www.endless-sphere.com/w/index.php/Potentiometer_(Pot)

 

[atom1025]

Thank-you much!

So based on that I determined that orange(1) is ground. Brown (2) is signal. Red (3) is positive.

So can you help me understand which wire is which coming out the controller?

I get two voltages. 5.1v and 4.9v.

The positive is a dead give away but not sure on the other two.

Adam

 

[amberwolf]

That part I dunno for sure, as they vary.

But if you measure from controller's battery negative to each of the three throttle wires, you'll find one has 0V. Then another has around 5V, and another should have less, or none, but might flicker around. The 5V will be power to the throttle, 0V ground, and the lesser V the signal, most likely. So assuming you measured yours that way already, the higher V is power and the lower is signal input.


Here's a catch, though: If you use a resistive throttle on a typical ebike controller, it will have a pretty big "dead zone" at the start and end, and a fairly narrow range in the middle that actually controls the motor speed. Most ebike controllers these days expect a hall throttle, which might output 0.9-1.4V at it's bottom end (off) and 3.5-4.5V at it's top end (WOT).

But a resistive throttle outputs from 0V to whatever voltage is at it's top (5V in this case).

So if the controller expects say 1.4V-3.5V for it's input, then the entire part of the throttle rotation for 0-1.4V is "wasted motion", then from 1.4V-3.5V it will increase speed, then no further increase from 3.5V-5V. Some controllers even have a protection so that if the throttle output goes over it's expected high end, it shuts off the controller--so the motor will stop powering the bike after you twist the throttle past that point.


If you look up "Magura" and maybe "voltage" or "voltage divider" in the forum search, you'll find a number of ways people have worked around this issue. (if you do find them, you are welcome to add links to them to the wiki article for pot throttles, for future questioners).

 

[atom1025]

Fantastic work men! Thank-you all for the knowledge.

Plugging everything in for the first time was nerve racking. I altered so many wires that I was nervous of mistakes. I plugged in the batteries and twisted throttle, motor spun up!

I'm happy!

Adam