Golf Cart Paddle Shifter

Thread Starter

TribbleRED

Joined Apr 1, 2020
5
Yup, you read that right... paddle shifters on a golf cart :cool:

***Disclaimer***
Out of respect for you boys and girls I have spent quite some time trying to figure this out before coming here so as to refrain from a drive-by post where the answer could have been found had I tried a little harder. Second, "Golf Cart Paddle Shifter" is the subject of this part of the project and this is how the vehicle will change between forward and reverse. There may be "simpler" ways to shift an electric vehicle but that is not the subject of this particular project. Any help as to the desired config would be appreciated.

Original Config:
Fwd/Rev switch on cart is a simple on/on spst switch, i.e. 2 hots and a common.

Outline:
I need to get two momentary switches at the wheel to signal a relay(s) to close in fwd or rev but never simultaneously both. Using one momentary switch is a no-brainer but I can't seem to wrap my head around assigning one momentary to each and force open its opposite. Another example: selecting one of two momentary switches will always signal to latch closed one of two contacts. The second momentary will always signal to latch closed the second of two contacts. Both switches will signal to close their respective circuits while forcing its counterpart open so as to not have both circuits closed at the same time - the latter being a project requirement.

I feel like there is a simple answer for this that I am just not seeing...

Additional:
I have 12v and 48v with which to work( (1) 48v bay, (1) 12v bay, & (1) 48 to 12v step down). That being said I BELIEVE the switch operates on 48v but I don't know just yet for sure... easy adjustment though after I know how this needs to be configured.

Extra credit: If you know of a good supplier for wide selection of din mountable 30A+ solid state DC relays that would be awesome.
 

Thread Starter

TribbleRED

Joined Apr 1, 2020
5
****NEW DEV****
I have talked this over with a friend and we have decided that for ease of operation we will just go with a single paddle(momentary) that will do it. However, I am still very curious how the aforementioned project could be completed with two momentary switches like that.
 

Alec_t

Joined Sep 17, 2013
11,146
Why replace a simple On-Off-On non-momentary switch?
If you use momentary switch 1 to latch Forward and momentary switch 2 to latch Reverse, how do you plan to reset to Off?
 
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iimagine

Joined Dec 20, 2010
479
Here is my solution:
SW1 -On SW2 - Off
SW1 - Off SW2 - On
Holding down either SW1 or SW2 for a predetermined amount of time and release: SW1 - Off SW2 - Off
 

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Alec_t

Joined Sep 17, 2013
11,146
Unless I'm mis-reading that circuit I don't see how the possibility of both latches being on simultaneously is prevented? Perhaps a couple of steering diodes could be added to do that.
 

iimagine

Joined Dec 20, 2010
479
Unless I'm mis-reading that circuit I don't see how the possibility of both latches being on simultaneously is prevented? Perhaps a couple of steering diodes could be added to do that.
The 100k common emitter resistor prevent both latches being on simultaneously. However, if both switches were to be pressed at the same time, both will be on at that moment and there will be a problem. For LED, it is fine but not for this application. Thanks for pointing that out.
NOTICE: Do not use that circuit!
 

ebeowulf17

Joined Aug 12, 2014
3,274
I don't have time to work out details or sketch schematic right now, but it seems like an up-down decade counter could be set up pretty easily to move between reverse, neutral, and forward, with two paddles incrementing in the two directions.

CD40192BC looks like a possibility at first glance, although I have negligible experience with counter circuits, so I could be way off base here.

Two output pins would drive forward and reverse relays, and one output pin (neutral) would drive nothing. Forward and reverse pins might also need to feed diodes or transistors in such a way as to defeat extra paddle bumps and set the end points.

If one of the more experienced members thinks this makes sense, feel free to run with it. If it's complete nonsense, let me know. If I don't hear anything either way, I might try to sketch and/or simulate this tonight or tomorrow when I have more time.
 

Audioguru again

Joined Oct 21, 2019
1,289
I have never been in a golf cart.
Isn't it bad to suddenly switch the direction of a golf cart? Shouldn't the cart slow down before switching direction, maybe with a delay?
 

iimagine

Joined Dec 20, 2010
479
Circuit in post #5 have a problem when both buttons being pressed at the same time, so a new solution is that when this happen, both output will be off.
SW1 - On SW2 - Off
SW1 - Off SW2 - On
SW1 - On SW2 - On - Both Off
 

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Thread Starter

TribbleRED

Joined Apr 1, 2020
5
I have never been in a golf cart.
Isn't it bad to suddenly switch the direction of a golf cart? Shouldn't the cart slow down before switching direction, maybe with a delay?
The controller on the golf cart does not allow the cart to engage if the motor is turning in an unfavorable direction. That is a feature already built into this and many others for just the reasons you think. Even in a slow roll it won't engage until stopped or very close to it.
 

Thread Starter

TribbleRED

Joined Apr 1, 2020
5
Circuit in post #5 have a problem when both buttons being pressed at the same time, so a new solution is that when this happen, both output will be off.
SW1 - On SW2 - Off
SW1 - Off SW2 - On
SW1 - On SW2 - On - Both Off
Very interesting. I will take some time to wrap my head around this.
 

ebeowulf17

Joined Aug 12, 2014
3,274
I finally got around to trying out my counter idea, and it was getting really complicated, so I switched to a flip-flop circuit instead.

I think this circuit gets the job done. Two of the resistors and capacitors on the inputs are for signal conditioning/noise immunity and may not be needed. Beyond that, it's a pretty simple circuit, with a flip-flop doing the logic and latching work, and a Darlington transistor (TIP120 probably) and a mechanical SPDT relay doing the switching.

Disclaimer: I haven't built and tested this circuit, and in fact I've never built any circuit using a flip-flop, so I can't guarantee anything... nevertheless, I'm pretty sure it all makes sense and would be pretty easy to put together.

***EDIT: Thanks to some good points raised by @Audioguru again, plus a few observations of my own, I've updated the schematic. Please see post 19 for the new and improved version.

golf-cart-paddles-CD4013-01.PNG
 

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Audioguru again

Joined Oct 21, 2019
1,289
You need to power the CD4013 and add a supply bypass capacitor close to it.
You also need to disable the second flip-flop in it because all Cmos inputs must go somewhere.
 

ebeowulf17

Joined Aug 12, 2014
3,274
Most ICs in simulations are not powered and work fine, even when they are VERY overloaded. Lots of magic. ;)
I forgot to give you credit earlier - while I disagree with your obsessive need to point out that ICs are unpowered in simulations (when you obviously understand what's going on there,) you are correct to point out that adding decoupling power supply caps and providing connections to unused inputs to prevent them from floating are both critical. While they're obvious to experienced builders, they may not be obvious to newer builders that we're often sharing circuits with. Also, I had neglected to look at the output capabilities - now that I've checked it, I'd rather spec a MOSFET instead of the Darlington so that I don't have to split hairs wondering what the relay coil current draw is, and therefore how much base current the Darlington would need. Also, I forgot to show a flyback diode on the relay coil.

So, with all those things in mind, I've updated the circuit with the electrical changes, as well as a number of notes on implementation. Here's the new and improved version (it still uses magic power, but at least there's a note explaining the magic!)
golf-cart-paddles-CD4013-02.PNG
 

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