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Author Topic: Question about Controlling Solenoids with Relays!!  (Read 963 times)
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Hello everyone, I am a beginner Arduino programmer and building a Robotic Arm using magnetically coupled rodless cylinders. The device will be powered by compressed air and controlled by solenoid valves via ATmega2560.

So far I have the control software written, and am relying on a relays to control the solenoids. But I am worried that the board will not provide enough current to the relays.

Here is a link of the relays: http://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Electro-Mechanical_Relays/Square_-z-_Cube_Relays,_Plug-In,_3A_-_15A_(78x-z-_Qxx-z-H78x_Series)/General_Purpose,_3A,_5A,_10A_(QL2_-z-_QL4_-z-_QM2_-z-_QM4_Series)/QM4X1-D24

If these are requiring too much current, does anyone have a viable solution to the low current supply (~20mA) from the arduino board.
Also using limiting sensors to tell the solenoids when to turn off.

As a beginner any help would be greatly appreciated, hopefully I can control these 24v solenoids via Arduino.

-Celex
 
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I don't see anything in that link for the current the coil pulls.

A good items to use might be some 2N3904 transistors though. They are pretty cheap and easy to come by. Lots of examples on here about how to use them to control relays.
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Hello everyone, I am a beginner Arduino programmer and building a Robotic Arm using magnetically coupled rodless cylinders. The device will be powered by compressed air and controlled by solenoid valves via ATmega2560.

So far I have the control software written, and am relying on a relays to control the solenoids. But I am worried that the board will not provide enough current to the relays.

Here is a link of the relays: http://www.automationdirect.com/adc/Shopping/Catalog/Relays_-z-_Timers/Electro-Mechanical_Relays/Square_-z-_Cube_Relays,_Plug-In,_3A_-_15A_(78x-z-_Qxx-z-H78x_Series)/General_Purpose,_3A,_5A,_10A_(QL2_-z-_QL4_-z-_QM2_-z-_QM4_Series)/QM4X1-D24

More importantly this appears to be a 24 volt coil relay? You can't wire that to an arduino 5 volt output pin and expect it to work. You require a transistor between a arduino output pin and a 24vdc relay coil and a 24vdc voltage source. And if you are going to use a transistor you may as well have the transistor drive the solenoids directly.

Lefty


If these are requiring too much current, does anyone have a viable solution to the low current supply (~20mA) from the arduino board.
Also using limiting sensors to tell the solenoids when to turn off.

As a beginner any help would be greatly appreciated, hopefully I can control these 24v solenoids via Arduino.

-Celex
 
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South Louisiana
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More importantly this appears to be a 24 volt coil relay?

Good catch, i looked right over that little bit of really important info.
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I found the datasheet for the QM4x1-D24 relays.

http://www.automationdirect.com/static/specs/qmrelays.pdf

There is a lot of provided information here. I'm not sure what I should be looking for.
In other posts I think I've seen people calculate minimum current requirement to turn on the relays by using the electromagnetic voltage requirements and resistance using Ohm's Law.

Does anyone know what voltage / resistance I should use on the sheet? Or which current tells me the minimum to turn on the relay from my Arduino mega.
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Coil Specifications
36.9mA @ 24VDC
Min. Operating Voltage - 80% of the rated coil voltage (24 * .8 = 19vdc minimum voltage to coil)

You cannot drive this coil directly from your arduino in any case.

the rating for the above mentioned 2N3904 is 200ma (if memory serves) so it would drive this relay fine.

Don't forget to research what resistor you need between the Arduino and the base of the transistor to avoid an over current situation on the output pin when driving the transistor.
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