Author Topic: VIC card operation  (Read 2206 times)

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VIC card operation
« on: March 18, 2011, 02:04:48 am »
While working out the routing of the various circuits in the VIC card,I have found that there are four op amps on the one end of the board.Three of these op amps are shown in the schematic,and the fourth one is not.The very first one of the op amps, the one closest to the tabs that plug the board in,is not in the schematic,and gets a signal from some source,and the second op amp gets a signal from the GMS control panel circuit Analog Voltage Generator.Now these two signals come into the coil pack through the nine pin connector and pass into this board.What I have found is that the first two op amps are wired in parrallel and go into the third one.There seems to be two different signals coming into these first two op amps,and are being joined.
 
Ok so my question to you all is, what other signal could be coming into these op amps? What purpose would it be to join two signals together through op amps?
 
Don

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Re: VIC card operation
« Reply #1 on: March 18, 2011, 04:49:44 am »
Hmmm...thats interesting Don. I'll think about it and see what I can come up with.

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Re: VIC card operation
« Reply #2 on: March 18, 2011, 05:34:13 am »
Hey Don,
I looked over the circuit and this is what I've come up with. There are 3 OpAmps on the Voltage Amplitude (fig 4) and theres also one on the Analog Voltage Generator (fig 3) and I think the one on fig 3 is on the vic card and this why u have to signals going into that OpAmp...one signal from the RPM Idling and the othere from the Analog Voltage. I think he just mounted the four OpAmps on the VIC card. If you have photos of fig 3 you should check and see if theres an OpAmp on the other side of the "Manual Speed Cal." and the "Run Accelerator" switch. Check that and let me know if this is correct.

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Re: VIC card operation
« Reply #3 on: March 18, 2011, 11:50:44 am »
Tony,there are five opamps in total.The voltage generator card had it's own opamp.So there is one opamp not in the schematic.
Don

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Re: VIC card operation
« Reply #4 on: March 19, 2011, 10:04:26 am »
Hi Dynodon, Im try'n to learn myself about opamps thru some stuff on this site:
http://www.bcae1.com/opamp.htm
Tony's great at that stuff :)

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Re: VIC card operation
« Reply #5 on: March 19, 2011, 21:11:34 pm »
Well what this part of the circuit does, is obvious, it is an "inverting summing amplifier". Which means, that it sums up the two inputs. Why he used two inputs, instead of the one in the patent Fig 4 is another question. Both inputs first have a voltage follower for decoupling and then they both go with the same resistance in the inverting summing amplifier. Which means, their input is added equally (summed up).
Maybe he just wanted to have the option to be able to have different circuits telling the VIC at which voltage it should run. If he used it is another question. Did he wire both of the OpAmp inputs to the Sub-D Plug?
But all in all, I don't think that this is really an important point, as it only controls the analog voltage level.


IMHO the really interesting part is the workaround he did with the comparator input, and the fact that he routed 3 different signals from the Q8-region to the connector. The big question is, which signal did he really use to drive the TIP120? And the other question: Where does the red wire, which is connected to the neg of the primary (by the blue wire), really go? It looks like it is going where actually one of the resistors should have been soldered. But it looks like this resistor was not soldered, but instead the ground connection of it was used for a capacitor and the other connection for the red wire. If it was really connected like that, then the actual circuit is a completely different one!!! It would behave completely different, than the one in the patent circuit!

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Re: VIC card operation
« Reply #6 on: March 20, 2011, 00:07:20 am »
Kali,both signals come into this board via the sub-d connector through pins 7 & 8.Now the signal from the analog voltage generator has the first OpAmp inverting that signal before it goes into voltage amplitude control.Then it gets inverted back when it passes through another OpAmp.What would happen if the second signal didn't get inverted before going into the the OpAmp that is in parallel with the the other signal?Would that make a differance on what comes out of the voltage amplitude control?
 
As for the red wire soldered onto the connection tab,it is the 12 volt input,and it goes to a place on the board labeled FUSE.From there it goes to the master on off switch,and on through the fuse.The trace where the red wire is soldered to the connector is cut.Thats why the small blue wire is there.The blue wire is 5 volts and is powering that heavy trace,and not the red wire.
 
The wiring is just as the schematic shows,and there is only one signal going into the Tip120.
Don