At 10:07 PM 8/15/2012, you wrote:
>Hi,
>
>I've got one more motor to get working on this oven (the one that runs
>the conveyor), but this one is an A/C motor...
>- Out the side of the motor near the head are white, yellow and black wire=
s.
>- Black and white go to a motor control board.
>- White and yellow have a 5uf 250V capacitor across them.
>- Two blue wires from the encoder on the back of the motor, also going
>to the motor control board.
>- Oriental motor (the manufacturer) has verified it's an A/C motor, most
>probably induction, but the motor is not easily accessible, so I can't
>get at a model number right now.
>
>However, I'm more interested in the controller (
>http://tinyurl.com/bvqdpgf ), and how I would interface with it...
>- Encoder signal gets modified a bit and then sent to a main processor
>board.  No prob with that.
>- 240VAC goes into the motor control board.
>- 3 wires go from the motor control board to the main processor board -
>W/Gy, W/Bk, W/O.
>Also, see here... http://tinyurl.com/d9jqnc3
>
>Those last 3 wires are the ones of interest.  The motor control board is
>pretty simple, and I've traced a bit of the circuit, to discover that
>the 3 wires go through/to a diode to ground, some trim-pots, and then to
>the input of an op-amp, so it looks like it's taking an analog input
>from the main processor board, then using the encoder feedback to tweak
>that for a specific speed.
>
>But I'm not sure I should just apply a voltage (even small) to it until
>I understand it better and am a little more convinced of it's input
>signal.  I'll draw a portion of the input circuit later.  Is there some
>standard for controlling this?  Anyone seen this before? Or is there
>some relatively safe way to test this?
>
>Thanks,
>-Neil.

Is the processor board 'hot'? I don't see any isolation from the 240VAC
mains.

I'm guessing that's a full-wave SCR phase control with tacho feedback
driving your 2-phase motor. Consider this "ramp and pedestal" circuit.

http://www.mi.mun.ca/users/rmatchim/assign/e1100/triggers.pdf


Which uses an obsolete UJT rather than the PUT (it sez) in your board,
but the principle may be the same, with the addition of feedback
from the tacho.

Best regards, =20

--=20
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