Controlling a linear actuator with a joystick

Thread Starter

asallwey

Joined Feb 2, 2017
11
I have a 4 direction momentary spst joystick. I also have several Bosch type relays, spst. Can I use these to change direction: up/down & left/right? I can make it work 1 direction with 1 relay, see attached. I found an old thread here where the person did it with spdt relays and a spst switch. Do I need to get spdt relays? I plan to use 1 fuse from power and a diode on each relay. Circuit help would be appreciated as this is not my skill area.
 

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MaxHeadRoom

Joined Jul 18, 2013
19,968
Usually a linear actuator only has two directions, extend-retract, you can use each position to pick up a separate relay.
presumably the other 2 positions are a separate actuator?
Max.
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Usually a linear actuator only has two directions, extend-retract, you can use each position to pick up a separate relay.
presumably the other 2 positions are a separate actuator?
Max.
Yes it has 2 directions. I have 2 and will use 1 for up/down and 1 for left/right (of a snowplow on my garden tractor). I figure if someone can help with the circuit for 2 directions I can duplicate it for the 2nd actuator.
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
[/QUOTE]
This is one possible circuit. The two pole center off switch may or may not work with your joystick.[/QUOTE]

Each direction movement engages the contact, so I guess it works like (or is?) a spdt switch. This circuit looks good, except I just have spst relays at present. It doesn't look like the 87a contact is doing anything since ground is also going to 85. So would my spst relays work if I wired them the same way?
 

drc_567

Joined Dec 29, 2008
772


This diagram shows the de-energized double throw relay. Note that contacts 30 and 87a are connected when the relay coil is off, and contacts 30 and 87 are connected when powered on. ... OK to use the single throw version.
... Since this will be battery powered, there could be a problem with sparks across the 30 to 87 contacts as the relay is de-energized and the contacts are opened ... basically a sort of current inertia effect. Place a 1N004 diode, or similar part, so that the negative terminal is connected to contact 86 and the positive end is connected to contact 85, in reverse bias. The diode negative terminal has the band marking around it. ... Necessary for each relay coil.

Here is a more complete discussion of these relays:
http://www.the12volt.com/relays/relays.asp
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Ok that clarifies things. I'll do a test with the spst relays I have. I was planning on using a diode, but had not identified one to use, so that helps a lot. That link was good, I'm saving it for reference.

Alex



This diagram shows the de-energized double throw relay. Note that contacts 30 and 87a are connected when the relay coil is off, and contacts 30 and 87 are connected when powered on. ... OK to use the single throw version.
... Since this will be battery powered, there could be a problem with sparks across the 30 to 87 contacts as the relay is de-energized and the contacts are opened ... basically a sort of current inertia effect. Place a 1N004 diode, or similar part, so that the negative terminal is connected to contact 86 and the positive end is connected to contact 85, in reverse bias. The diode negative terminal has the band marking around it. ... Necessary for each relay coil.

Here is a more complete discussion of these relays:
http://www.the12volt.com/relays/relays.asp
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Just a quick question. When I googled the 1N004 it comes up as a 1N400_. If you meant 1N4004, I think that is a 400v, 1a diode. Is this right? In my research I saw recommendation that the diode ..."can size the diode by taking these voltage and current values and adding 20 to 50 percent for safety." Using this statement, the 400 volts is good, but since the actuator can draw up to 5a, the diode should be rated closer to 10a.

Just learning here, thanks again.




This diagram shows the de-energized double throw relay. Note that contacts 30 and 87a are connected when the relay coil is off, and contacts 30 and 87 are connected when powered on. ... OK to use the single throw version.
... Since this will be battery powered, there could be a problem with sparks across the 30 to 87 contacts as the relay is de-energized and the contacts are opened ... basically a sort of current inertia effect. Place a 1N004 diode, or similar part, so that the negative terminal is connected to contact 86 and the positive end is connected to contact 85, in reverse bias. The diode negative terminal has the band marking around it. ... Necessary for each relay coil.

Here is a more complete discussion of these relays:
http://www.the12volt.com/relays/relays.asp
 

drc_567

Joined Dec 29, 2008
772
Just guessing actually. If you wanted to be precise, start off with a larger diode ... say use the 1N004, rated at 4 amps, and see if you could measure the current in the circuit as the relay opens. Essentially, the purpose is to dissipate the energy stored in the coil in such a manner that the coil itself is not damaged. An analogy might be using the brakes at the wheels to stop a moving vehicle, as opposed to stopping it by running it into a tree.
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Ok, thanks again. Now I know a way to evaluate the diode. Time to go test things. :)

Just guessing actually. If you wanted to be precise, start off with a larger diode ... say use the 1N004, rated at 4 amps, and see if you could measure the current in the circuit as the relay opens. Essentially, the purpose is to dissipate the energy stored in the coil in such a manner that the coil itself is not damaged. An analogy might be using the brakes at the wheels to stop a moving vehicle, as opposed to stopping it by running it into a tree.
 

GopherT

Joined Nov 23, 2012
8,012
1N400x diodes (X = 1 to 7) are generally rated for 1 amp and increase in voltage with value of X. Look for another diode series if higher current is needed.

NOTE: 1N004 is not a valid excuse diode part number.
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Ok, played with this a bit and still need a little help.
My observations:
++ The diagram shows a spdt switch. My joystick is basically several spst switches, so that's not an issue I think.
++ The diagram says that the "actuators ground through the relays".
++ The diagram shows the actuator has 1 lead from each relay powered when the switch points to a given relay.

My actuator has a red & black wire. If I connect the case to ground and either wire to +, I get nothing. I need to connect to both actuator wires for movement, and reversing is done by reversing the leads.

I'm not seeing how the diagram's left relay is reversing voltage, which is what I would need.
 

drc_567

Joined Dec 29, 2008
772
It will be necessary to modify the original circuit. Use two of the relays for the UP motion, and two for DOWN. Where the battery connects to both contact 30 terminals, separate the wires so that the relay on the left connects to the + battery terminal, and the relay on the right connects to the - battery terminal. The other modification that is necessary is to connect a wire from the up/down switch DOWN terminal to contact 86 of the relay on the right, so that that the relay on the right now activates simultaneously with the one on the left. There is now a connection between the appropriate actuator lead and ground.
Doing this gives you a functional circuit for the DOWN motion. In the same manner, use two additional relays to construct the UP circuit.

Try this out and see if there are any conflicts ...
If you need a diagram ...
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Thanks! Ok, back to the bench to play some more!

It will be necessary to modify the original circuit. Use two of the relays for the UP motion, and two for DOWN. Where the battery connects to both contact 30 terminals, separate the wires so that the relay on the left connects to the + battery terminal, and the relay on the right connects to the - battery terminal. The other modification that is necessary is to connect a wire from the up/down switch DOWN terminal to contact 86 of the relay on the right, so that that the relay on the right now activates simultaneously with the one on the left. There is now a connection between the appropriate actuator lead and ground.
Doing this gives you a functional circuit for the DOWN motion. In the same manner, use two additional relays to construct the UP circuit.

Try this out and see if there are any conflicts ...
If you need a diagram ...
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Your recommendation worked.

This has been quite a learning experience. What has become very obvious is that I pack away my spst relays since I want to control 2 actuators with my 4-position joystick. To get all directions I would need 8 relays, and there isn't a lot of spare room on my garden tractor, plus I only have 5 on hand. It's time to get some spdt relays and follow tried-and-true methods, like the diagram you posted and others I have run across.

Thanks again for your help!
 

Thread Starter

asallwey

Joined Feb 2, 2017
11
Ok, I have my spdt relays, and have one last question.

What size diodes should I put across my relays for a 5a max 12v DC linear actuator?

As I said in #8 above, a guideline I found said to add 20 to 50 percent to the highest amp and voltage of the circuit. DRC_57 in #9 recommended a 4a unit, then measuring the current, and I assume, making a change based on ... .

I have the following 2 ratings: 3a 200piv and 10a 1000piv. What is the downside to using the 1000piv diodes? They are bigger but physically fit.

No longer have a Radio Shack around here so I tend to use ebay. A 20% greater amp rating has me looking at a 6a unit, not too many there but a couple at 600v or 800v.

Thanks again!
 

drc_567

Joined Dec 29, 2008
772
Glad to see everything is going together ...

Actually, by placing almost any diode across the coil, with the negative end towards the positive terminal you have created a path for the current to re-circulate, in a loop, going through the coil, and then through the reversed diode, and circulating around that loop until the energy is dissipated within secondary resistances. The point being that with the reversed diode in place, no extreme voltages will be generated as the relay contacts are opened,
So as a good guess, just use the diode with the lowest voltage rating. The 200 PIV, 3A diode should be fine. To see if the coil energy is being successfully dissipated in the diode, operate the relay a few times, then place a test finger on the reversed diode to see if it is noticeably warmer ... which would be a result of dissipated coil energy ... The energy of the magnetic field created by the energized relay coil.
 
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