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Supreme Being
Group: Administrators
Last Login: Monday, October 31, 2011 9:18 PM
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Junior Member
Group: Forum Members
Last Login: Friday, February 12, 2010 12:20 PM
Posts: 21,
Visits: 122
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| Thanks! So I need to connect the Signal pin and Gnd pin to the 2 ends of coil of a 5v relay, right?
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Supreme Being
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Last Login: Friday, April 22, 2011 6:18 PM
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HI,
The way I read your question about hooking a relay directly to a gpio
is a " DO NOT! ".
Most relay coils draws more than 25mA ( which is the maximum ) current
a GPIO line can sink. I dont see anywhere on the Serializer that there is
any buffer between the PIC IC and the GPIO lines.
DO use at least a simple transistor circuit to buffer between the relay
and the Serializer. Common small 5vDC relays typically draw about
100mA, 4 times the rating of the GPIO signal pin.
Don Lewis
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Junior Member
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Last Login: Friday, February 12, 2010 12:20 PM
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| Hi Don, thanks for the advice! good that I checked it before I actually put it together, lol. Can you recommend a simple circuit? Or any other simple way that I can throw a switch carries a 6v, about 1A (4 AA batteries) load, I'm not hardware savvy at all. I would imagine relays are very common in robotics, a little surprised that Serializer don't have any direct support for relays....
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Supreme Being
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Last Login: Friday, April 22, 2011 6:18 PM
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Hello Hexn,
Doesn't take much.
I haven't tested it, It should work fine as shown. It is available
all over the net roughly as shown. I just cleaned it up for
presentation. You are, of course, on your own as liability goes. 
Don Lewis
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Supreme Being
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Last Login: Friday, April 22, 2011 6:18 PM
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I should note: when gpio signal goes high (to 5vDC) transistor
turns on, pulls current through relay which energises relay.
The diode is for back emf protection for the transistor and
Serializer. If powering other than low voltage or low current
with any controller you should use optical isolation or other
means to protect the controller.
You can use the +5vDC and Gnd pins of the GPIO header
for those parts of the circuit assuming the relay is within the
power specification of the Serializer as Jason mentioned.
Don Lewis
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Junior Member
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Last Login: Friday, February 12, 2010 12:20 PM
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| Thanks Don. So basically I should use the Vcc pin of GPIO as the power source for the relay rather than using signal pin as a power source, instead, using sig pin to turn the transistor on and off thus turn relay on and off. Am I understanding it correctly?
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Supreme Being
Group: Forum Members
Last Login: Friday, April 22, 2011 6:18 PM
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You got it
hexn (1/22/2010)
Thanks Don. So basically I should use the Vcc pin of GPIO as the power source for the relay rather than using signal pin as a power source, instead, using sig pin to turn the transistor on and off thus turn relay on and off. Am I understanding it correctly?
Don Lewis
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