Relay not switching... - Raspberry Pi Forums
well went ratshack , picked 5v relay try control first relay via rpi, here parts.
275-0240 - 5v - spdt relay (http://htyp.org/275-0240_radio_shack_5-volt_relay)
npn transistor pack, (2n222a , 2n3904, 2n4401).
1k ohm, 1/4 watt, 5 % tolerance.
gpio -> 1kohm -> base of resister
transistor e -> ground
transistor c -> - coil
+ coil -> 5v
+ coil -> diode -> 5v
anyways, transistors work control leds require 2-3ma (i measured ma, via multimeter). relay clicks on if "ground" pin should going collector. if attempt "switch" relay via gpio hear faint clicks, relay not thing. when measured current draw of transistor relay hooked it, (and switched on via gpio, read 40~ma, if read current draw of relay connected directly ground (causing switch on) draw 84~mah.
maybe of more keen engineers can tell me have gone wrong? tests seem tell me transistors not big enough, means missing understanding of how these transistors related. also, tested make sure transistors getting saturated, , getting .71v , giving 3.3v not change brightness of led.
read through that, , bigger can set me straight. understand why transistor failing me.
275-0240 - 5v - spdt relay (http://htyp.org/275-0240_radio_shack_5-volt_relay)
npn transistor pack, (2n222a , 2n3904, 2n4401).
1k ohm, 1/4 watt, 5 % tolerance.
gpio -> 1kohm -> base of resister
transistor e -> ground
transistor c -> - coil
+ coil -> 5v
+ coil -> diode -> 5v
anyways, transistors work control leds require 2-3ma (i measured ma, via multimeter). relay clicks on if "ground" pin should going collector. if attempt "switch" relay via gpio hear faint clicks, relay not thing. when measured current draw of transistor relay hooked it, (and switched on via gpio, read 40~ma, if read current draw of relay connected directly ground (causing switch on) draw 84~mah.
maybe of more keen engineers can tell me have gone wrong? tests seem tell me transistors not big enough, means missing understanding of how these transistors related. also, tested make sure transistors getting saturated, , getting .71v , giving 3.3v not change brightness of led.
read through that, , bigger can set me straight. understand why transistor failing me.
a few thoughts circuit shown below?
transistor pack using?
relay trying drive on volatge on transistor base , collector?
collector voltage enable quick approximation of coil current.
have tried putting second 1k resistor in parallel existing resistor, giving 500r , more base current.
looks have used wrong transistor, , cannot drive enough current energise relay, or connection not think is.
transistor pack using?
relay trying drive on volatge on transistor base , collector?
collector voltage enable quick approximation of coil current.
have tried putting second 1k resistor in parallel existing resistor, giving 500r , more base current.
looks have used wrong transistor, , cannot drive enough current energise relay, or connection not think is.
raspberrypi
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