Actually, I’m a bit lost on this diagram.
Where’s the GND? And I’m not sure what switch the yellow is going to. The relays are the switch.
Sorry as I said it was for something else. Hopefully this will make more sense. The positive (red) relay 4 and negative (black) relay 1, comes in on the common terminal.
The orange jumpers from relay 4 feed one side of relays 2 and 3.
The grey/white jumpers from relay 1 to the other side of relay 2 and 3.
The yellow lines are the motor output connected to the common of relay 2 and 3.
This way power can only be on one side of the motor at a time.
You are on the right track with your relay logic but to ensure you don’t short it out during switching you can use a double pole (or more) relay. The ones shown in the posts above are only single pole which is why the examples use multiple relays. Get yourself a relay with more sets of contacts and you only need one… however, again as you mention, you wont have an ‘off’ position so using a second relay will give you the option to cut power completely.
If you wire as per my second example there is no position that can short the line. Even if you were intentionally trying to do it.
The double pole would be nice because one relay would switch both connections mechanically reducing the risk of shorting. Is there a double pole that can be used with ESPHome (Wemos D1 Mini or ESP8266, etc?)
Hmm…what about this:
3 relays with a crossover connection. First image would be NC and circuit would be controlled by 3rd relay. Disable circuit, then switch 1 and 2 to the open position to reverse the flow.
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Ok state 1 if you toggle relay 2 you will short to ground. If you want to do 3 relays you can do it like this.
All relays off = off (both motor legs to negative)
Relay 2 on = direction 1
Relay 1 & 3 on = direction 2
Any other combination will also be an off position. all on, 1&2 on, 2&3 on
I saw your other post, I’d connect them both to this one setup and use a rheostat on the faster motor. It doesn’t matter what side of the load it’s on. It’s something you’d set once.
True, if I toggle relay 2 I would short to ground, but, using NodeRED, I could program the logic to ensure that the timing is sufficient to ensure that relay 3 has opened the circuit to allow time for 1 and 2 to switch…but I do see the risk.
So, in your diagram, you have 12v+ connected to NC on relay 1 which energizes the 2nd relay’s open pin, so that means that relay 2 would need to be activated, while 1 and 3 remain de-activated. Then, to reverse polarity, I would have to activate relay 1 to send 12v+ to relay 3, and also activate relay 3 to complete the 12v+ delivery to the 12v- motor lead, and deactivate relay 2 to switch to the ground. (do I have it, or am I backwards?)
Then, if relay 1 were activated inadvertently, it would send 12v+ to a dead end at relay 3. Or if relay 2 were inadvertently deactivated, we would just have all 12v- connected to the motor with no complete circuit. I think I see…no matter what, if the relays are out of position, the worst that could happen is a dead end 12v+ or a 12v- loop of nothing.
So if the microcontroller lost power and the relays were all dead, but the 12v power supply continued to chug along, there would be no short and it would be safe.
Yes?
Regarding the rheostat, wouldn’t there be a potential of one of the actuators slowing down over time due to possible failure, or something of that nature? I suppose I would just re-adjust it.
What would be really cool is if I could measure the load on the actuators, use those sensors to calculate a digital adjustment to a digital speed control, and auto-calibrate (more work than it’s worth, but kinda cool.)
You would only be able to have a negative loop not a positive one. If you used 4 relays there would be a completely disconnected position available. That’s just for future reference. I’ve used a 4 relay setup for 220v gate operators in the past.
As for the rheostat it should be just a real slight adjustment, maybe would need readjustment. If it was more complicated like a curve then the on the fly adjustable would be great. Curve being a spot where the motor struggles more than at other points.
Any relay with a 5v coil will work with a D1 mini etc.
https://www.altronics.com.au/p/s4128b-2a-5vdc-dpdt-pcb-mount-telecom-relay/
Fusion360 doesn’t seem to have orange ;). Lol…well, yellow it is. So this is the setup now per your diagram. I’ve already ordered the 4 relay module since I’ll also be adding an LED strip that the 4th relay can turn on and off.
Thanks!
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I ran into a problem with the 3-relay setup.
The DC Motor Speed control that I have causes a short and kills the ATX power supply if the polarity is reversed. This happens if the speed control is connected between the relay and the motor. The only way I can get the speed control to work is to ensure that the input polarity on the speed control is never changed, thus, it needs to come before the relay power input, in which case, it will affect both motors on the 3-Relay setup.
So, I went with 5 relays. 2 Pairs of relays, each pair imitating a DPDT relay with the risk of shorting. To avert the risk, I added a 5th relay to kill the power completely between the power supply and the speed control, then setup NodeRED with logic that ensures power is off before the 4 relays are switched to reverse the polarity.
The worst that could happen is the ATX Power Supply will be tripped (as it has some sort of failover protection) and that would only happen if the 5th, or shall we call it, the 1st relay in the chain were to fail.
Either way, It’s working, and working well…and I’m only dealing with 12V, so it’s not a nuclear situation. ;).
This is the likely culprit. A rheostat (potentiometer) used in series with the motor supply is just a resistor. You would interrupt one line to the motor connecting to the center and 1 end pin of the rheostat. Your just creating a choke point in the power supply.
Hi @arretx ,
Were you able to finish your project? I was searching for something similar to use 3 bistable solenoids with a 4ch relay module.
Unfortunately these solenoid need an inverted polarity to turn off. At first I tought they would work with a normal signal input to either turn off and on.
So I was searching for a solution to reverse this 9v DC 
I was able to finish it. I ended up using 4 relays. One of the relays kills the power to the others so there’s no risk of shorting the connection, then I created a flow in NodeRED to manage the switching for the desk’s up/down functions.
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Four relay to drive one motor? Mmmm I should drive 3 solenoids and reverse polarity for them.
I bet I should find another way.
My mistake. 5 relays. One lone relay to cut power to the 4-relay module. The 4-relay module handles swapping the polarity of the connection to the actuators. On one of the feeds, there’s a potentiometer to control the speed of one of the actuators as it’s a bit faster than the other and needs to be slowed down to match.
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5, wow.
Well I need only on/off with a short+9v/-9v signal.
I will try with a motor driver 🤷
That is insane! I’ve posted a new topic with question how to control a “simple” fan that has three speeds:
low, mid, high - each wire is dedicated to single speed, so I cannot have two or three lines powered at the same time. Ideally three state(+ off) rotary switch, but “smart” and digital.
I really, really don’t want to build standalone demultiplexer with ESP that turns off three relays, waits 10ms (or according to the relay datasheet) and then turn on only the needed relay.
Do you have a shortcut and ready to buy device that I might need just to compile/flash and use it with Home Assistant?
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