Hope this helps, sorry for cockeyed drawing.
@JCA34F The drawing is wonderful, thank you! I get it now and was able to model that. As far as a complete double relay module goes the diode bridge is something I would want to make sure is built into the unit correct? All the units I've seen only have one COM coming out of each relay.
I found a descent diagram of the unit dlloyd suggested in the beginning and I have one of these modules in hand. Here is the diagram:
Will my wiring diagram work to provide forward and reverse motor control? It looks similar and I think I'm interpreting it correctly, not sure if I'm missing anything. Everything looks the same the wires are just moved around right? Is this even a proper schematic of the internals?
I should have drawn that so C+ and D- are connected to the left relay which only has 1 wire in each terminal so you wouldn't have to try getting 3 wires in the right relay's terminals. One other thing, I would connect the negative (-) power supply wires to the NC relay terminals so when both relays are OFF the motor lines will be connected to GND instead of 12V. But be sure C+ is connected to 12V+ and D- is connected to 12V-.
EDIT: On my first drawing, I drew the diode between B and D backward, sorry 'bout that.
I don't know if the tinkercad model is interpretable or if it's right but here's a picture of it:
Purple are the com lines. I have ground wired to the closed NC here, I messed that up in my drawn diagram. The motor turns as it seems it should. So, when the motor suddenly stops the magnetic field transiently continues to move and this generates a spike of currant in the line? But what I don't get is when the negative power supply wires are connected to NC, shouldn't any transient just flow through to ground. Am I trying to stop current from flowing back through the positive line? Or am I trying to dampen the currant? Will the diodes absorb current even if there is another path for it flow?
-RG
Actually, what happens in the case of the relays, is that the diodes carry the current while the relay contacts are moving in between the NO and NC contacts!
I'm not a big fan of these relays. The relay that had the proper wiring inputs with seperate grounds for power and control signal ended up having bad relays - these guys. I had two, one made a rattling sound and that relay didn't work. The other had one relay that made a crackling sound when it's circuit was powering the motor. I suppose I could find a better source.
The other relay that's in the picture from the op works with power from the MEGA but it seems it would share a ground with the arduino if I used a separate 5V supply. I don't know, if one I/O is on low does it act as a ground?
Note I haven't done any of the diode wiring, since I'm just testing my prototype on the mechanical side now.
Anyhow, I've been thinking that using an h-bridge motor controller might be the way to go. Initially I thought I could do without the LVM control, but there's an issue with the actuators I'm using. The actuators can jam if you run them without a load - they have a speed of 9"/sec. They also don't have the longest lifetime - 20k cycles. Why use these then? I could replace them several times and still be under the cost of a long lasting industrial linear actuator that meets my speed requirement - at least as far as I can find. Anyway, I was thinking if I run them without a load but slow them down as they approach the end of the stroke I could improve the life cycle by reducing the motor load and not worry about jamming.
-RG
After reading your last post here and the details in the other thread, I realized that I have something similar with with the same issues! Its a power barrow with a fork lift attachment that uses a 22-in linear actuator. It also jammed sometimes under no load. I took it apart about a year ago and adjusted the limits to activate a bit earlier in the travel. I don't advise doing this as it took far too much time and I didn't get 100% improvement. My workaround is to just use it within a shorter range of its travel and avoid use of the limit switches.
I think the limit switches are the weakest link and are probably why there's a 20k cycle rating. If keeping within the 20% duty cycle rating (4 minutes on, 16 minutes off) and avoiding extended use of the limit switches, I don't see why this couldn't last as long as industrial models, assuming they would have similar mechanical wear ratings.
Note that for the internal descriptions on page 8 of the datasheet, it lists 2 diodes (item 14). This is probably for kickback suppression.
Anyway, I was thinking if I run them without a load but slow them down as they approach the end of the stroke I could improve the life cycle by reducing the motor load and not worry about jamming.
I like this idea.
What if the relay module only switches under no electrical load conditions? Then the contacts would never arc or wear (pitting) as they would only be used to configure the power to the actuator and never to switch the power while live. Adding the mosfet module mentioned earlier to switch the DC negative on or off could accomplish this. It could (possibly) also be used to slow down operation using pwm at a 75% duty cycle (for example).
If you could use the actuator within (for example) 90% of its travel range and you know the time it takes for full travel, then slow mode could be used to reduce speed at each end (0-5% and 95-100% travel).
Also, maybe slow mode could be used to preset the actuator to a limit. For example, slow mode to the 0% limit, then slow mode back to 5%. This is for "calibration". Now both limit switches are closed. From here, you can operate at full speed from 5% to 95% (based on time) without tripping the limit switches and therefore extending the lifespan of the actuator.
