Relay control schematics
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Posts: 46,084
Ok, for all you Transistor Gurus out there, please reference
the "Relay Schematics.doc" file I uploaded. Circuit "A" is how I was
told to control a relay with a stamp. But the problem is, I'm using
SPDT Latching relays, and the set and reset coils have a common
ground. Therefore, if I hook up the way that was described to me,
triggering either transistor would trigger both coils. So I thought
up schematic "B", a modification that puts the NPN transistors on the
plus side of the relay coils instead of the ground side. The
question is, will it work the same? Will it work at all?
Thanks in advance.
Don
the "Relay Schematics.doc" file I uploaded. Circuit "A" is how I was
told to control a relay with a stamp. But the problem is, I'm using
SPDT Latching relays, and the set and reset coils have a common
ground. Therefore, if I hook up the way that was described to me,
triggering either transistor would trigger both coils. So I thought
up schematic "B", a modification that puts the NPN transistors on the
plus side of the relay coils instead of the ground side. The
question is, will it work the same? Will it work at all?
Thanks in advance.
Don
Comments
When the transistor turns on -- the base must be .7 Volt more positive
than the emitter to remain on. In this case you would need to bring the
base to 5.7 volts. The stamp is not capable of doing that. Using PNP
transistor would be the way I would attempt to do this task. Same base
resistors, connect the emitter of the PNP to +5V the collector to the
relay. Make sure the diode is biased so that when the relay coil is on
the diode is off.
HTH,
Leroy
mtlhead7 wrote:
>
> Ok, for all you Transistor Gurus out there, please reference
> the "Relay Schematics.doc" file I uploaded. Circuit "A" is how I was
> told to control a relay with a stamp. But the problem is, I'm using
> SPDT Latching relays, and the set and reset coils have a common
> ground. Therefore, if I hook up the way that was described to me,
> triggering either transistor would trigger both coils. So I thought
> up schematic "B", a modification that puts the NPN transistors on the
> plus side of the relay coils instead of the ground side. The
> question is, will it work the same? Will it work at all?
> Thanks in advance.
> Don
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statements need to be changed from HIGH Stamp Pin to LOW Stamp Pin to
activate your relay. With PNP transistors the base must be lower (more
negative) than the emitter to turn the device on! Therefore, a HIGH on the
base will turn it off and a LOW will turn it on.