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Tc9400 v to f opinion's please

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Hi Mike,

What comes out of the commercial controller? AC or non-filtered pulsating DC.

Full rectified but un-smoothed dc 120 c/s

Is there a reversing switch between the commercial controller and the track? Or is the reversing function built into the controller?

Yes. The polarity reversal DPDT is part of the controller and within its housing. Simple + and - connections from the controller connect to the track.

Can you post a diagram of your existing hookup (before you connect the VtoF)?

If you dont get it this time then yes!

Ok we have connected our controller to the track. Think of the track as a pair of wires or bus maybe.
Now we are aiming to monitor the voltage for input to the TC9400. Now, if we place a full wave rectifier between the track and the input to the latter what do we get? Basically 120hz unsmoothed dc or ignoring volt drops in diodes the same as we put in. Now we reverse the polarity to the track via the DPDT switch or swap the wires.What happens and what do we get now from this second bridge rectifier?

We still get a positive going voltage to the TC 9400 ! So polarity of the track voltage is irrelevant.

If you look back a few post's you will note that I mentioned the use of a common ground as opposed to using the ground of second bridge and possible implications.
Secondly I think it feasible to measure volt-drop across the second bridge and use this as an offset value (zero) on the TC9400. Just a thought.

Pse let me know your thoughts and if you still don't get it will post sketch.


Willy
 
Ok, here is what you are describing. As long as the controller/tracks are floating, you can define your "ground" to be the negative side of your second bridge. If you do, the signal out at V(a) and V(b) are identical regardless of the track polarity. I added some filtering, as before...
 

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Mike,
Many thanks for your time and interest. Yes you pretty much get the idea but if I may just a few questions,

Would It be more adventagous to use an op-amp for the filter?




How does the passive filter effect the input to the TC9400? I can only guess that we include the filter resistor when calculating input resistance.




It would be obviously beneficial to source the vcc for the TC9400 from a smoothed source. Can this and the input (from the bridge) share the bridge ground or would it be better if I provide a ground from source?


Thanks,

Willy
 
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