4 Channel Relay Module

[TandemDrip]

I was eager to test out the new 4 Channel Relay Board so I picked one up at Jaycar, provided it with 12 Volts (regulated) and started to provide 5V logic from my arduino... was all working fine, turning on relays on channels 1 and 2 until... 4 minutes later...

The relays are staying locked in the ON state. I have unpowered the module and re-powered it, but still, the LEDs for the first two channels remain ON.

There is no schematic on the web site so I can't really check whats going on but is anyone else having these challenges ?

Andrew

[jonoxer]

Hi @TandemDrip,

That sounds very odd. The board is pretty simple and just uses FETs as low-side drivers, so there's not much to go wrong unless the FETs have been blown. Thanks for the prod about the schematic: we don't even have a product page up for it yet because that device is so new, but I've made the GitHub repo public so you can see the schematic.

https://github.com/freetronics/RelayModule4/

When you say the LEDs for the first 2 channels remain on, is that even when there's no input to those channels at all? What happens if you connect 12V to it, but leave the inputs floating?

There is a pull-down resistor on each input to hold the FET off unless it's specifically driven high, so if the output is on even when the input is unconnected it sounds like there's something wrong with the module.

If you don't get it sorted out we'll replace it under warranty of course, but I'd like to understand what's going on.
--
Jon

[TandemDrip]

Hi Jon,

Yes, the LEDs remain on even with the input lines floating. I have tried it with the remaining two channels and get the same problem. After a few minutes of operation, the LEDs remain on - without any load and with the inputs floating. Dead FETs is my guess too. I'm only driving 12 volt reed relays What are the FETs rated too ? Thanks for the link - I will have a look at that today.
Regards,
Andrew

[jonoxer]

Thanks for the update, Andrew. Driving reed relays should be a walk in the park for it! I'll do some testing myself tonight and see if I can come up with a reason for the failure.
--
Jon

[marc]

Hi Andrew,

I've been running a test of a RELAY4 here today to try and duplicate this, and no trouble yet at least. I'm driving 12V coil relays, have a 12VDC supply into the RELAY4 and EtherMega running the test, and using digital output pins to control the RELAY4 input lines.

Would you be able to send some picture(s) of the setup that you have that's doing this? It would be really helpful to understand the connections, board and wiring setup, thanks.
I'm interested to see also how the GND and relay output pins are wired, especially if there's a floating GND that drifts the control pin voltages up high enough to trigger them.

FYI the mosfets are NXP 2N7002, this exact part:
http://www.nxp.com/documents/data_sheet/2N7002.pdf
Marking "12W". They should be more than up to the job, 300mA 60V rated, and we have strong diode protection intended to withstand driving big relay coils and loads.

Thanks, look forward to hearing from you
Marc

[Felshrimp]

I'm having the same problem with my 4 Channel Relay, altho the only one its done it on so far is No.1

[CyberFonic]

I've just bought a 4 chan relay module. I'm retrofitting into an existing 24v DC (regulated) situation and can only have five wires in the cable connecting the relays. Would the module still work fine if I common the Vcc (relay V+) and drive the relays from the V- outputs. The cable is about 1.8m long and shielded. My logic is that it should work ... but ...

BTW, has the problem with stuck channels been resolved? or at least the cause identified??

Cheers,
Eugene

[jonoxer]

Would the module still work fine if I common the Vcc (relay V+) and drive the relays from the V- outputs.

Perhaps I'm being a bit thick today, but I'm having trouble following that description! Any chance you could draw a diagram and take a photo, or something like that?

BTW, has the problem with stuck channels been resolved? or at least the cause identified??

So far we don't know that there is an actual problem in the first place, because we haven't had enough detail provided about how it's hooked up for the people who say it's not working. Our best guess is a floating ground, but without a diagram or a photo of how it's been hooked up when misbehaving we can't tell.
--
Jon

[CyberFonic]

I've pretty much answered my question on the weekend. Downloaded the schematic and saw that the V+ lines are commoned on the board. So I've attached the relays as shown on the schematic (sorry about my shaky mouse hand drawing). So far it's working fine.

BTW all those LEDs make testing so much easier. Great feature!

[jonoxer]

That diagram is fine, it makes it clear what's going on!

Yes, the relay + supply is common with each relay switched on the low side. The way you have it hooked up is good.
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Jon