8574 I/O extenders solved
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Posts: 46,084
I've solved my problem with the relay driver issue for the output of
the 8574. The 8574 outputs ground, so I found out what was wrong with
my use of a pnp transistor to amplify 9v for controlling a relay.
(out from 8574) C
+(RELAY)-
GROUND (9
VDC)
Ground
B ( )
E
+ 5VDC
|
|____ +9 VDC
Instead of making ground common between the two power supplies, I
made positive common. The output from the 8574 is ground, and the
5VDC and 9VDC sources are connected positive to the emitter. The
collector outputs +9 VDC to the relay, and the negative terminal from
the relay connects to the GROUND on the 9VDC power supply.
Now granted my terminology is probably all wrong here, but the
application works.
the 8574. The 8574 outputs ground, so I found out what was wrong with
my use of a pnp transistor to amplify 9v for controlling a relay.
(out from 8574) C
+(RELAY)-
GROUND (9
VDC)
Ground
B ( )
E
+ 5VDC
|
|____ +9 VDC
Instead of making ground common between the two power supplies, I
made positive common. The output from the 8574 is ground, and the
5VDC and 9VDC sources are connected positive to the emitter. The
collector outputs +9 VDC to the relay, and the negative terminal from
the relay connects to the GROUND on the 9VDC power supply.
Now granted my terminology is probably all wrong here, but the
application works.