What to do with GND/COM jumper - 12v pwr supl 8ch relay board, Arduino Uno r4 two DC motors

Projects General Guidance
1

Hi guys!

This is my first post and in gonna be 100% honest here. I'm building a remotely controlled motorized clamshell dome for my telescope. It's been one insanely huge project so far. The done is done, all the mechanical engineering is done, the belt system thats driven by two DC motors is done. What's left is the in my opinion overly complex part of controlling the shells that glide over each other to fully open the dome and to close it.

I have purchased:
Arduino Uno R4 WiFI
Luxorparts 8ch relay
Mean well 12v 26.7a powersupply
And I have the two DC motors. They are actually 24v but I have tried a few times to get this working but I have messed up two times and long story short one 24vpowersupply and two relay boards are now in EL-heaven :backhand_index_pointing_right::exploding_head:

I did the H-configuration wiring, compiled a code with help from AI and it worked. I could open and close the shells and I thought I was all good I could run the DC motors separately, forwards and backwards..

the next day I was gonna work out some konkurs on the mechanical side of the system and find out exactly how long my motors had to run to open and close perfectly, but after a few runs, one of the motors just continues to go with no response when trying to stop it.. after examining the relay board I found some bad thing.. long story short, I don't know what the hell I did wrong. I'm thinking maby, my 24v connections to the relay was a bit loose?

I have now purchased a new 8ch relay board, and I have went over the wiring, and made sure it's alle 100% but I get stuck at one point. My 8ch relay board don't have a JD/VCC pin. It have the VCC,GND,in1-8 AND GND/COM pins Wich have a jumper on them. Im guessing maby my mistake was to leave this on?

I hope someone can please help me out here because I'm really pressed for time her... I'll attach a bunch of pictures.

If something is unclear. What I'm wondering is Wich pins do I use FROM the Arduino Uno board, what do I do with the jumper, and how do securely and safely use my 12 powersupply for this project? :hot_face::smiling_face_with_sunglasses:

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2

Why not post a link to that relay board...

Also your relay outputs are wired the way they could never switch anything...

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Be honest! What is your expectation for the life of this project?

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Do you really mean that? Because I did use this configuration with the relay board that got burnt.. and it did exactly what it should? It drove the DC engines forward and reversed them. So I don't know what you mean now? If you notice I have legge the COM terminal open on all relays. That's where I'm gonna pute the positive and negativ of the two DC engine, but since the motta are outside I. The done, it's kinda hard to connect them.. and I was going to make sure Evry thing is right before I even connect the 12v.

5

Hm.. the life of this project what does that mean?.if you are asking about how long it will last? I'm planning to open the dome 1one time when I'm using the telescope and close it after the session is over. And hopefully there will be 3-4 nights a week for a couple of months.. and after that I don't think it will be used mouch for about a year..

I'm not that good a sarcasm, so if you are trying to be a wiseguy.. why do you even bother.. I came here to get some helt with how I sadly use the relay to use the 12v powersupply.. what's the big deal?

6

Her is a link for the relay module:

7

  • This 4 channel board is probably similar to your 8 channel board.

  • For isolation, the jumper would be removed.

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8

That obviously change everything, I don't know every pass you will do in future.
That relay module is little bit weird, but with 5V Arduino Uno you can use it like that, with jumper attached.

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The way I read it is:

COM + IN1 thru 8 - for connecting the Arduino GPIO pins to the opto-isolators.
GND+VCC - for external power supply to drive the relay coils.

The relays seem to have flyback diodes so back EMF should be dealt with. The jumper seems to be providing an option to common the Arduino ground with the DC supply ground but its probably not necessary. Why go to the trouble to opto-isolate the inputs only to then create a common ground path?

The marking on the top of the relay show that they are rated to be driven using 5V. I can't be sure from your comment whether this was the case, but unless the board has a regulator (online photos of similar boards suggest not), then it shouldn't be being run off a 24V supply?

Its a little unclear form the your comment what had actually failed, but is the circuit powering the DC motors off a separate supply to the relay board? Also, since you appear to be running them in both directions to open/close so do you have a bi-directional Trazsorb (TVF) diode across them to suppress back-EMF? If for some reason you were running the motors on the same DC supply as the relay board and without any back-EMF protection then back-EMF might also have contributed to the problem.

This is all speculation because we can't see how you have everything connected. Could you show a diagram (photo of sketched one is fine) of your wiring please?. It will be useful for helpers to provide more specific advice.

(Just noticed the diagram posted by @LarryD which crossed with my post. A picture speaks a 1000 words. :grinning_face:)

10

What are your motors' full load and stall current? We need a full wiring diagram

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Thanks alot for friendly answers.

I feel kinda dumb for beeing so deep in with things I really don't know to much about.

I can draw up a diagram, but I don't think I can do that until tomorrow.

But for now: I really don't know what optoisolation even means.

But they way Im Thinking of doing this project is this:

I have the two DC motors. They came from a motorized hospital bed and the tag on the motor covers said 3.5A 24V. But when I measured the voltage of that system it was actually running at 40V

On the motors thenself they say 24v L59A30

So I'm not entirely sure of what's right for these motors.

I'm going to use a meanwell 12v 26.7a powersupply

And the relay to turn the. On/off and forward and revers.

What I did do was to power the Arduino uno R4 with barelejack 12v 12.5A and used the 5.5 and GND from Arduino board to VCC and GND to the relay board. And I used pin d3,d4,d5,d6 at the Arduino board to in1, in2, in3 and in4at the relay board. I left the jumper on, I did not touch it.

From the 12v power supply splittes the + four ways, and did the same with - and I wired the relay board as shown in the pictures I attached. And I put 1 DC motors + in COM on relay 1 and the - in COM on relay 2. And I did the same for the second DC motor.

I have adhd and not the best memory chip installed in my head, byt if Im not mistaking, that was all I did..

And for clearing it up once more. I have bubble and triple checked this over and iver on youtube and multiple places on forums etc, but I can't seem to find a straight answer on what to do with the com/VCC jumper. And the 5v VCC and GND from Arduino.

I hope I make myself clear here, and I want to thank you guys so much for your time and interest to help! :+1:

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Here is one motors markings

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A3.5 Amp inductive load is too much for those CS Songle relays, I wouldn't expect much life from them. You DO have kickback diodes across the motors?

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Oh man...really? But they are marked 10A? 230v 10a and 30V 10a??

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And no.. I don't have kick back diodes.. I think I read something about it some where.. so will that help my case? It's like some kinda of protection from "backfire" right?

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That is telling me your relays will NOT work properly. That is telling you it will draw 59 Amps from a 24V power supply when stalled and starting. When running under full load it will draw 30 amps.

You really need a 60 Amp 24V power supply to power the motors if both run at the same time. That will require something in the 10AWG wire size range.

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  • For reversing motor direction.

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Yes, I mean the life of the project. It seems to be spread around an area and will not be in continuous use. But you will spend a lot of time trying to figure out why it doesn’t work right.

Your use of relays and especially a bunch of relays soldered into a single circuit board.
You could and should be using H-bridges to control your motors, since they do not have moving parts that will fail.

My experience with the blue relays stem from a project when I owned an electronic assembly service. I modified a commercial 12 volt Peltier cooler/heater to store solder paste and then warm it before use. It used a programmable timer, not an Arduino. Several time one of the blue SPST relays failed and I sawed the cover off to see the problem. Welded contacts, trash between to the contacts. And the contacts were two hemispheres for contacts, so the actual electrical contact was tiny, not near the rated current.

So that is why I asked about the expected life of your project. You can make it easy and very reliable or you can make it a pain to maintain.

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You can replace those super cheap relays with the equivalent Omron brand relay.
https://www.digikey.com/en/products/detail/omron-electronics-inc-emc-div/G5LE-1-E-DC5/1277875

https://omronfs.omron.com/en_US/ecb/products/pdf/en-g5le.pdf

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I'm planning to run one motor at a time. And they will run for about 4-5seconds.

Can you supply me with a bit more info about your suggestions. I'm all ears to learn what will be the best solution! :+1: