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Topic: Arduino Uno, Relay shield - relays not picking (Read 3894 times) previous topic - next topic

Richter12x2

I recently picked up this relay shield- http://www.ebay.com/itm/221342495715?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

The issue I'm having is: 
Case A:  I can get the input LEDs to operate appropriately (light constantly when I push a momentary button), but they won't activate the relay. 

OR 

Case B, I can get the relays to engage, but not disengage, and the input LEDs don't go fully dark.

Case A:

Here's a description of the connections:
Arduino powered from 12V External

VCC on Shield is connected to 5V Arduino
JD-VCC on Shield connected to V-In on Arduino (12-VDC)
Ground on Shield to Power Supply side Ground on Arduino
Input1 on Shield to Pin 12 on Arduino

Connected this way - the Input LED on the Shield cycles with the button push, but no click or continuity from the Relay


Case B:

VCC on Shield is connected to V-In on Arduino (12-VDC)
JD-VCC on Shield is jumpered to VCC

This way, the relay is energized immediately, and pushing the button makes the led on the shield dimmer, but doesn't turn off, and relay remains energized.

Is there something else I should be doing?  The code is obviously working as it should, but I'm no EE, the lack of a biasing resistor on my momentary button threw me off for the longest time.

Any help would be greatly appreciated!

MarkT

Well the schematic is provided which is good, however its incorrect(*), which is bad.  It looks like your case A is
the one you should be using, but you will have to measure the current to see if the opto coupler
is getting enough.

Connecting as your case B sounds like a good way to fry your Arduino - never put 12V on an Arduino pin.

(*) relay coil bypassed by a short circuit!!
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

knut_ny

VCC on Shield is connected to 5V Arduino
JD-VCC on Shield connected to V-In on Arduino (12-VDC)
Ground on Shield to Power Supply side Ground on Arduino
--------------------------------------------------------------------
!! coils dont like 12V
replace jumper 5V JDUcc
Keep 12 on load  side only

Ny

Richter12x2

I guess my confusion was that, since the auction has them listed as 12vdc relays, and each relay is rated for 30vdc or 120vac at 10 amps, then that meant the supply side of the relay wanted 12v to energize the coil.
It makes sense not feeding more than 5vdc to the arduino pins though, because that's what the voltage regulator would deliver.  So my interpretation is that

jc-vcc = 12vdc (from v-in of 12V supplied Arduino)
vcc = 5v from Arduino
ground = power supply side ground of arduino

Now I just have to figure out why the relays won't engage with the status LEDs

knut_ny

read on relays.  You may be correct ..  It says 5V  .. or 12 V
(mine are driven with jumper in place)
---- it thay are 12V - then remove jumper and feed 12V to JCVcc
Ny

Richter12x2

Getting 12v should be easy enough, because they're going in a car anyway - I just can't figure out why the optocouplers aren't activating with the 5v.  I'm driving myself nuts with alligator clips though - going to go out tonight and get a proto-board, so hopefully this will be easier to prototype and measure.

Also going to move it from my Uno to one of the little Leonardos that it will live on in the car - we'll see if that makes any difference.

knut_ny

opto  5V OK if not burned by 12V feeding, but you cant observe it unless you feed power to phototransitor (voltage read on relays)
(common GND)
Ny

Richter12x2

Just finished talking to vendor - testing without Arduino we saw that the relays picked with 12v on VCC and jumper on - but the relays would not trigger with less than 8vdc on VCC, even with a brand new one off the shelf.

Which (if I understand correctly) means that would be 12VCC feeding back to Arduino through the input pin, so it seems these relay boards can't be used with Arduino without some additional circuitry between them.

Oh well, you live you learn.  It's not like they're super expensive to begin with.  I just ordered a couple of the 5VDC relay boards that will hopefully get my project done.

Thanks for your help, everyone!

knut_ny

#8
Feb 20, 2014, 10:17 pm Last Edit: Feb 20, 2014, 10:55 pm by knut_ny Reason: 1
.. I still belive that those (12V coils) relays can be used with arduino. The 5V and 12V side are electrically separated by the optocouplers. (In your case.: accident..)
.. Are there 510 Ohm resitors ?.. add 150 Ohm in parallel

The schematic shown (web-address above) is not correct as it shows a non-working unit.
The lower on in this drawing will work
Ny

Richter12x2

As far as I could tell, the issue was that 5v wouldn't activate the optocouplers - I may have a go at swapping them out at some point in the future, because I also have a 4 relay module, so with 8 optocouplers I could potentially save 3 modules for future use.

knut_ny

,,or add parallell resistors to 510 ohm to manage the leds (inside optos) to switch the transistors.
(180..270 ohm)
Ny

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