Anyone try driving a relay with two output pins.
#1
Posted 19 October 2012 - 01:56 PM
#2
Posted 19 October 2012 - 02:03 PM
ARM-based microcontrollers generally run at 3V3 and output 3V3 logic.The other thing I still cant figure out is why its 3.3v output, when the industry uses 5v makes it harder to work with.
If you need 5V output, I'd recommend adding a transistor to your circuit (although I'm guessing you've already done this).
Glad to hear that your optical relay solution is working. Cool.
Chris
#3
Posted 19 October 2012 - 02:09 PM
Edited by neslekkim, 19 October 2012 - 02:10 PM.
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Asbjørn
#4
Posted 19 October 2012 - 03:11 PM
Arduino digital pins are 5v from what I understand, I don't know about the other ones. Either way the 3.3 or 5 its very low to work with.I have looked at the ULN2003V12 7-Channel Relay and Inductive Load Sink Driver it a nice chip does all the work for you, and if you get real lazy zzzzzzzz There is a real nice 16-Channel 12V Relay Module. For PIC ARM AVR DSP Arduino MSP430 TTL Logic
P.S.
Thanks for the info on the transistor going to build my own board someday
#5
Posted 19 October 2012 - 03:36 PM
#6
Posted 19 October 2012 - 03:36 PM
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Asbjørn
#7
Posted 19 October 2012 - 03:37 PM
They're also moving towards 3.3V. Some products are already 3.3V, and they added the IORef pin so they can switch voltages later too.Arduino digital pins are 5v from what I understand, I don't know about the other ones.
Arduino boards that already run on 3.3V: Arduino Fio, Arduino Pro and Arduino Pro Mini.
Also, if a relay works on 5V, there's the maximum of amperes a pin can handle. Relays often pull quite some amps. That's why a transistor circuit can be very useful.
The board you're showing looks very complete. Including transistors. So I think it'll be fine. To be sure, I recommend to check the datasheet of the board.
My .NETMF projects: .NETMF Toolbox / Gadgeteer Light / Some PCB designs
#8
Posted 19 October 2012 - 04:02 PM
#9
Posted 19 October 2012 - 04:29 PM
#10
Posted 19 October 2012 - 07:43 PM
#11
Posted 13 November 2012 - 09:05 PM
#12
Posted 13 November 2012 - 09:48 PM
If I'm using a dual coil latching relay with voltage of 3V (with coil resistance 129 ohms), do I need to use the transistor ??
It's a bit touch & go with your situation. When they say 129 ohms, they mean total impedance. Part of it is reactive and the other is purely resistive. 129ohms at 3.3V from the CPU pin will draw up to 23mA which is borderline. If you intend on driving the relay in short bursts then it would possibly be acceptable but otherwise you wouldn't.
Once the transient behaviour dies away from switching the relay on, the effective impedance of the relay will be less and you'll exceed the maximum continuous current draw from the CPU pin and smoke the poor thing.
If it was me, I'd use a transistor.
#13
Posted 14 November 2012 - 03:22 PM
It's a bit touch & go with your situation. When they say 129 ohms, they mean total impedance. Part of it is reactive and the other is purely resistive. 129ohms at 3.3V from the CPU pin will draw up to 23mA which is borderline. If you intend on driving the relay in short bursts then it would possibly be acceptable but otherwise you wouldn't.
Once the transient behaviour dies away from switching the relay on, the effective impedance of the relay will be less and you'll exceed the maximum continuous current draw from the CPU pin and smoke the poor thing.
If it was me, I'd use a transistor.
Is there any example code for using a relay?
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