Because it's a zero-crossing detector. The voltage on the + input sets the threshold.
As you vary the voltage on the + up or down, you should see the position move on the input waveform.
Yes. The simulation confirmed my suspicion that the G888 is not doing peak detect and my original goal was to mimic the G888 board so in that sense it is interesting that the G888 is no better than the circuit I already have in place. I am bit curious why DEC are not doing peak-detect in Dectapes. Maybe the design with redundant pairs of read heads makes it unnecessary?
The offset circuit was deliberately left out in the simulation since the input signal was centered anyway.
You will also notice that the G888 self-oscillates if the input signal goes to zero. This is intentional and is used
for the up-to-speed circuit.
I cannot find any noise source in the simulation program so I think it could be difficult to get it to oscillate when simulating
Hi All;
Here are the Last three Pictures..
THANK YOU Marty
Thank you Marty! I will try to simulate those when the on-line simulation service starts working again. (They better start fixing their server in Bangalore or I switch to something else)
Do you know what bit rate this interface was targeted for? I was unable to catch that in the pictures you attached. Was 1kbit/s, 10 kbit/s or 100kbit/s. It is good to know when setting the input signal parameters.
The reel motor driver described in 4196375 is the one used in the TS04/TS11. The read amps don't look like 4315220 though.
Agree, the peak-detector in the TS04 is indeed quite different. I looked through the schematics for the ones I found after a quick look at bitsavers, TS04, TU16, TE16, TS03, TU58 and Cipher F880. None of them seems to be using such a circuit as in the patent. My initial testing of the circuit in the patent indicate that it needs some work to get it less noise sensitive. Pity that the on-line simulation doesn't include a noise source so I could elaborate more on this issue in the simulation. It would be nice to find a real world example where it (or some other good circuit) is used.
I started off trying to simulate the quite simple circuit of the TE16. Much simpler than the circuit of for example TU16. I am not sure what purpose jumpers W1 and W2 has. Maybe it just for testing? They are not mentioned when quickly glancing in the maintenance manual.
Unfortunately the simulation always gets stuck at 2%.