Relay board?

[chuggins143]

I'd have to assume the relays use DC for the coils, but if there was an problem wouldn't it cause issues with the relay board itself rather than making it all the way back to the hub and messing with the signal from another unit?  ...and since I'm using this same setup with other controls systems, why wouldn't I be seeing it with the other systems?   I'm switching the same types of loads with them without issue. 

[Wayne.C]

Best guess is that some sort of electical disturbance from your setup is being coupled through the USB and causing the problem.  I'm guessing that the actuators have some sort of motor that is being energized?   You might try a USB isolator as a test.

I just finshed troubleshooting a problem with a USB device in my lab that kept dropping out everytime I fired up a variable frequency drive.  Noise from the drive was being coupled through a power meters RS232 port into my USB-232 adapter.  Messed up all USB devices including the mouse.  Looks like I need to order an isolated USB-232 adapter.

[chuggins143]

Ok, after actually downloading the manual for the relay board, they suggest a MOV for AC inductive loads...  and since I'm switching what is nothing more than two AC motors on/off I'm thinking this might be the problem.  Is there some way to size MOV's for the application based on voltage, current, or something?? 

[chuggins143]

...and once I have them, where is it best to mount them?  At the motor end or at the relay end?  I only ask because I have about 25 ft of cable between the relay and the motor.

[AnalogKid2DigitalMan]

MOV's are typically rated for a given clamping voltage, then by energy dissipation required.

Here is an app note:

http://www.littelfuse.com/data/en/Application_Notes/ec608.pdf

You want to mount them at the source of the spike, probably right at the motor end.

-AK2DM

[chuggins143]

Thank you very much for the info!  I will put it to good use.

Chad

[JÞB]

Just chiming in-

Iv'e used the ERB 24 and its big brother the ERB-48 (47 relays).

Take a good long look at the relays on the board-  the orig MFG of the relays has folded and replacements are getting scarce.  I ecpect MCC will be struggling to put out a new rev of the product in the near future.  On this app- it might be better to "Roll-your-own" board.-- just saying

[chuggins143]

Really not what I was wanting to hear....   but thank you for the info!  I'm in the process of building a new lab and will be needing several of these units for my controls... maybe I should order them now.  I haven't seen the 48 relay board, but I'll look into it!

Thanks,

C

[JÞB]

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@chuggins143 wrote:

Really not what I was wanting to hear....   but thank you for the info!  I'm in the process of building a new lab and will be needing several of these units for my controls... maybe I should order them now.  I haven't seen the 48 relay board, but I'll look into it!

Thanks,

C

---

Sorry bout that-  thought I'd point it out though.  Maybe the relay specs can be transfered to another MFG facility- I dunno.

[chuggins143]

No apologies necessary... not your fault.  Not like you went and closed down the plant.  It just makes me a little apprehensive about planning my build around their hardware when it may go away... or be unavailable when I need it.  

You guys have any kit suggestions if I want to DIY it? 

Thanks,

Chad