I’m planning out a control system using 16 PA-15-11 high speed linear actuators from progressive automations for a maze that can change it's configuration. The actuators will be pushing up and bringing down small 10" high X 6" wide walls in the maze. The controller I want to use is a MEGA2560 R3. I intend to power the actuators with 5 Mean Well LRS-350-12 power supplies. 4 of the power supplies would provide power to three actuators and one power supply would power 4 actuators - Note that no single power supply would activate more than two actuators at the same time. Also, in total No more than 4 linear actuators would need to be triggered at one time and they could also be staggered in their activation. I will probably take the actuators past the end of their life (20,000 cycles) but never come close to exceeding the duty cycle of 20% (4 minutes on, 16 minutes off). Finally, I don’t need any speed control of the motors, I just need them to extend and retract at their specified operating rate.
To control power and direction of the actuators I am considering two options. One would be to use a 2-channel relay unit - something like this NOYITO 30A 2-Channel Relay Module. relay spec. Wired in this manner for one actuator:
I would draw from the LRS-350 to power the relay, but I'm not sure the way I'm doing it is safe. I'm planning on making a power supply box that includes the relays that stands next to the actuators they power and control. Also, I’m still trying to figure out how to wire this up so there is no back current. How do I know if the relay module already provides back current protection? Seems like these components never have specs for the build, just for the components.
Two would be to use a dc motor controller. I was thinking of this Pololu unit or this Cytron unit. Seems like this option is a lot less fuss, but these share a ground with the MCU. Do they only share a ground with the control circuitry? Seems crazy that they would share a ground with the motor power supply, but is it really crazy with a good circuit design? I also want to know if I can use DIO on the LVM input since I don’t need any speed control of the linear actuators? If I was limited to only LVM inputs, I would exceed the MEGA LVM output channels.
Wow, if you made it this far thank you for reading this! If you have input to share I thank you again. This is a project I'd love to share freely, possible caveats and all, when I get it up and running. I’m still figuring out what I don’t know, and discovering what’s wrong with what I do know. It’s taken me a few weeks just to formulate this question. Any input is greatly appreciated. Also, thanks for the input so far from my previous posts.
First- in general you want all grounds connected together. That is the reference point for everything.
Most relay modules have a flyback diode on the relay coil. But since the control is through opto-isolators, then you have nothing to worry about.
I am not following you wiring of the actuator. Do you have the actuator in hand? Do you reverse it by simply reversing M+ and M-? How do you know when it's reached the limit of travel?
Also, do I read your description correctly? Your actuator is larger than the walls you are moving? How heavy are the walls? To move a 10x6-inch wall, you could use a much smaller servo motor.
This is not specifically your module, but it is typical of relay modules:
@SteveMann All grounds? Shouldn't the grounds for MCU and the actuator be seperate? Shouldn't those be two seperate circuits.
The actuator is getting input from the two COM outputs on the pair of relays I posted a link too. The wiring diagram includes the actuator, relay module, power supply, and arduino. A HIGH signal from one DIO arduino input moves the actuator in one direction and HIGH signal from the other DIO input moves it in the other direction.
I have the actuators, they have a 10" stroke. The walls get pushed up from below the floor and the maze floor is elevated. The walls need to move fast so a servo motor won't do as far as I'm aware, and the weight has been accounted for, all of that is fine. They're plexiglass walls.
I don't like that kind of relay module, they SHOULD have a separate connection for the opto coupler common, but that would cost the mfgr another 3 cents.
@JCA34F I'm actually trying to figure out the details of the power situation and it is something I forgot to include. I plan to have the MEGA connected via USB. Will I run out of power to communicate with the relays? I may add IR sensors to the maze as well. I left that out to limit the complexity of my post. I just wanted to focus on powering and controlling the actuators right now.
I don't understand how the diodes will work with diagram I have. If I put diodes on the lines running to the actuator from the relay wouldn't that only allow the motor to turn in one direction?
Isn't there a separate connection for optocoupler common on the relay I provided a link to? On the MCU input side of the relay module there is DC+ and DC- for the relay power. Then there is the CH1, CH2, and COM. Isn't that COM running back from the optocouplers? It serves as the ground coming from CH1 and CH2 if I understand correctly.
Also I have a relay with 5v input for testing, with that I could provide power to relay from arduino without an issue correct?
OK, here's a cockeyed hand drawn diagram, hope you can read it, think I would go with a single TVS diode connected right at the actuator terminals if possible.
@JCA34F Thank you for the diagram. It makes sense to me. I'm learning about TVS diodes now. When you say:
TVS diode connected right at the actuator terminals if possible.
Do you mean on the relay side or as close to the DC motor as I can get them? I'm trying to figure out if this protection is built into the actuator. At first glance from the documentation it doesn't seem to be.
My thinking is:
If the diode is located at the relay and the cable to the actuator is 1 meter long, the spike current will have to travel the cable and create a magnetic field that will be radiated from it.
If located at the actuator, it will be absorbed right there, less radiation antenna.
Of course, there are differing opinions.
@JCA34F I can buy that. I do want to minimize any sort of noise in the area. I'm not sure to what extent I'll have to go, I'll chase that issue if it becomes a problem. Putting a TVS diode close to the actuator wouldn't hurt.
