Remote control of rheostat (or motor)

Thread Starter

almiller

Joined May 20, 2022
9
I'd like to build a remote control to regulate the speed of my electric golf cart and I'm looking for suggestions.
I'm a hw novice (more a sw guy) but willing to learn attempt this if it's possible.

The golf cart speed is controlled via a rheostat and knob on the handle.
When I'm walking the course I'm constantly micro adjusting the knob to get the speed right
which means I have my hand on the handle all the time.

The rheostat only has 3 wires that go to the motor. I'm not sure how it actually controls the speed.
What I want is a remote device with 3 buttons, faster, slower, off which is all that the rheostat
seems to do. It tuns clockwise, counter-clockwise, and clicks at the end to stop the motor.

Thanks.
Alan

rheostat.png
 

MrSalts

Joined Apr 2, 2020
1,762
So, to be clear, are you asking...
For some type of wireless control of your golf kart's speed?
Or
For some method to move this potentiometer to a new position in the cart?
 

Alec_t

Joined Sep 17, 2013
12,807
Welcome to AAC!
A 'click' at the pot travel end is unusual for a 3-pin pot.
The pot setting almost certainly adjusts the duty cycle of a PWM speed-controller. What markings are on the pot?
 

Thread Starter

almiller

Joined May 20, 2022
9
So, to be clear, are you asking...
For some type of wireless control of your golf kart's speed?
Or
For some method to move this potentiometer to a new position in the cart?
I want some way to control the speed of the cart through a (wireless) remote.
 

MrSalts

Joined Apr 2, 2020
1,762
I like the bottom one of you want to simply attach the rotor on that one to the existing "rheostat" (potentiometer) on your cart.
You can use some electrical tape to couple the two knobs/rotors together for a quick/easy try. Not bad for a $40 attempt.
 

Thread Starter

almiller

Joined May 20, 2022
9
And here's the control unit on the cart that I'm trying to modify. Cart only has one motor (m2 +/- outputs) but the control unit has 2 unused pinouts (m1 +/- top left).
kart.jpg
 

Thread Starter

almiller

Joined May 20, 2022
9
The Lejin remote controller doesn't come with a motor. If I understand the description this wont allow me to control the speed of my motor it will simply turn the motor on or off and forward and reverse. The Lejin has 2 modes momentary & latch

Setting the control mode Momentary
Press and hold button 1 of transmitter: motor rotates in positive direction. Release the button, the engine stops.
Press and hold button 3 of transmitter: motor rotates in reverse direction. Release the button, the engine stops.
Press and hold button 2 of transmitter: motor stops.

Setting the control mode Latch
Press button 1 of transmitter: motor rotates in positive direction.
Press button 3 of transmitter: motor rotates in reverse direction.
Press button 2 of transmitter: motor stops.
The 2nd one appears to be able to control the speed of the speed of a motor by regulating the output power.
DC Motor Speed Controller Universal DC 6V 12V/24V Speed Controller Digital Display with IR Remote For Car Truck Motor Driver Heater Controller
 

MisterBill2

Joined Jan 23, 2018
11,877
I am just seeing this thread for the first time. What it seems like is that you want to be able to start the golf cart going without your hand on the handle, which I am guessing is also used for steering the cart. In that case remote operation can be rather deadly.
 

Thread Starter

almiller

Joined May 20, 2022
9
I am just seeing this thread for the first time. What it seems like is that you want to be able to start the golf cart going without your hand on the handle, which I am guessing is also used for steering the cart. In that case remote operation can be rather deadly.
Hi MisterBill2, yes but it's a push cart. I expect to be walking alongside the cart (5 to 10 ft away). I just don't want to have my hand on the handle constantly micro-adjusting the speed. The rheostat knob that controls the speed is super sensitive and to get the correct speed requires a 2 mm. turn of the knob. It's a pain in the ass to be constantly micro adjusting the dial when the cart is driving over bums, wiggling, shaking etc.
 

vu2nan

Joined Sep 11, 2014
232
Hi Al Miller,

You may use a 433 MHz, 12 V, two-channel, wireless relay module with a remote (key fob).

The relays are to have DPDT contacts.

1.png

The existing speed control potentiometer is to be replaced by the modified one.

The resistor values are to be so chosen that (R1 + R2 + R3) = R, the value of R1 gives the required low speed and that of (R1 + R2) the required high speed.

The values are to be measured at the existing potentiometer terminals, using a multimeter, with the knob turned to the positions which give the desired speeds.

The 'NO' contacts of relays A & B select 'high' and 'low speed' respectively (by actuating key A or key B on the remote).

The 'NC' contacts in series select 'zero speed' (when the keys A & B are both released).

Nandu.
 
Last edited:

Thread Starter

almiller

Joined May 20, 2022
9
Hi Al Miller,

You may use a 433 MHz, 12 V, two-channel, wireless relay module with a remote (key fob).

The relays are to have DPDT contacts.

View attachment 267860

The existing speed control potentiometer is to be replaced by the modified one.

The resistor values are to be so chosen that (R1 + R2 + R3) = R, the value of R1 gives the required low speed and that of (R1 + R2) the required high speed.

The values are to be measured at the existing potentiometer terminals, using a multimeter, with the knob turned to the positions which give the desired speeds.

The 'NO' contacts of relays A & B select 'high' and 'low speed' respectively (by actuating key A or key B on the remote).

The 'NC' contacts in series select 'zero speed' (when the keys A & B are both released).

Nandu.
So this solution would only allow me to set 3 states and not allow me to "gradually increase or decrease speed"?
1. run motor at high speed
2. run motor at low speed
3. run motor at 'zero speed'
 

MisterBill2

Joined Jan 23, 2018
11,877
To make holding the desired speed easier one option would be a lower-value pot wired as a rheostatin series with the top of the present speed control pot.
To prevent deadly remote operation, which door should he get in if he's a left handed hitter?

View attachment 267865
I was imagining a heavy industrial motorized cart. One that might carry half a ton of small castings in one load. Golf carts are different. Not nearly so able to do great harm.
 

MisterBill2

Joined Jan 23, 2018
11,877
DD got it right in post #15, thanks for the drawing. An added variable resistance to allow finer adjustment. Not original with me, it has been done and published for at least 50 years that I am aware of. The resistance of the added pot should be no more than 10% of the existing one. And the switch is not really needed, just turn the fine adjustment to the end and it will not have any effect. The challenge will be in the finding a place to add it.
Total remote radio control could also be used but it would be a lot more complex, and cost a lot more. And those robot golf carts include a distance-keeping scheme that is quite impressive. I think that they use IR and a passive reflector system. Rather safe because they stop if they lose contact.
 

MisterBill2

Joined Jan 23, 2018
11,877
OK, it seems that I missed the part about the small golf cart. I was also considering one of those ride-in ones. What can I say? I never claimed to be infallible.
 

Thread Starter

almiller

Joined May 20, 2022
9
I dismantled my motor and the control box to measure & understand how the speed of the motor is controlled.
Now I think the problem is that my motor (or the Rheostat) which is limiting me in adjusting the speed.

I measured the voltage going into the motor while slowly turning the rheostat from no-power to full-speed.
I can see that the voltage increases in only 5 steps at 4.0, 5.3, 6.6, 8.9, and 11.2 volts.

Is it correct that the change in voltage is what is changing the speed here?

If so, perhaps what I need is
  1. a remote with 2 buttons (plus and minus) that sends a signal to a receiver
  2. a receiving unit (arduino+motor shield) to increase/decrease the voltage going to the motor.
 
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