Zero Crossing help

[Matt]

Neither of my two Ren64s are working.

According to a PIC with the diagnostic code, everything is working fine except the zero-crossing signal. I have no idea where to go from here, but here is what I have:

- The power LEDs on both the Ren64 and the Ren-T are lit.

- I built my own Ren-T on a breadboard. The transformer is a radio shack 273-1365 (http://www.radioshack.com/product/index.jsp?productId=2103732&cp). I have tried building it twice over with no luck either time. I used the parts list on the Wiki (http://christmasinshirley.com/wiki/index.php?title=Ren-T_Assembly_Instructions) (D1, D2, D3, R1, R2).

- On the Ren64, I've populated R9 and Q1. I checked continuity and everything has a good solder connection.

- J2 on the Ren64: the shunt is between pins 1 and 2 (closest to the PCB edge).

Any ideas on what I am doing wrong or what I should check next?

Thanks,
-Matt

[RavingLunatic]

- J2 on the Ren64: the shunt is between pins 1 and 2 (closest to the PCB edge).



Really that is pins 2 and 3, with that in mind which pin of the RJ45 IN connector are you bringing in your ZC. It should be 7/8 not pin 3

Do you have an oscilloscope to see what the ZC coming out of your version of Ren-T looks like?

[Matt]

Yes, power (+) and ZC are on 7/8.

I was thinking the same thing - I wish I had an oscilloscope, but I don't. Any other advice?

-Matt

[Wayne J]

Yes, power (+) and ZC are on 7/8.

I was thinking the same thing - I wish I had an oscilloscope, but I don't. Any other advice?

-Matt

Is your ren-T built following this schematic?
http://christmasinshirley.com/wiki/images/5/5e/Transformer_pcb_sch_002.GIF

[Matt]

Yes.

-Matt

[Matt]

Any other ideas?

Since I'm in a pinch...
Could I use my sound card as a scope, similar to this:

http://www.instructables.com/id/Cheap%2c-Easy-Light-Probe/

How much in current limiting resistors would I need to limit the voltage so as not to fry my sound card? (I am using a 12.6V transformer with the circuit above, and the limit for a sound card is around 2Vpp).

-Matt

[RavingLunatic]

Matt,

I tried out those instructions on that website and to my surprise it works (kinda).

I can't seem to figure out the oscilloscope features in the Visual Analyser software but the spectrum section seems to work well for seeing the ZC signal.

I hooked up to the Ren64 at R9 (Q1 side) and it seems to be a small enough signal that I didn't damage my sound card.

I can clearly see a peak at 120 Hz, so that would be what you would want to see if you decide to go that route.

[Matt]

Well, I tried out the makeshift oscilloscope and I got this. This is from the Q1 side of R9. Can anyone tell me what to make of this?

Thanks,
-Matt

[xmus]

Assuming you are showing us the ZC signal.... have you captured anything you know works? For example, have a look at the OSC output with your scope or the serial data in.... I guess I'm asking, do you have confidence that what you captured is actually a fair representation of what the signal looks like?

Also, 60 Hz would have a period of 0.017 seconds... so if you wanted to catch say 4 of these on your display, you would need your timescale set to about
.06S/20 = 0.0033S = 3.3miliseconds.... looks like your squares are closer to 50mS... you need to increase your resolution I think.


Also, can you get voltage on the X axis?

[RavingLunatic]

See if you can change the frequency range on the spectrum display.

Try having it only show for 0 - 300 Hz

You should see a spike at 120 Hz. Notice in my pic the main signal at 120 Hz and the 1st harmonic at 240 Hz.

I see spikes on your current pic that could be the harmonic but you really need to see what is going on in the 60 to 120 Hz range.

BTW: I got a much nicer oscilloscope signal and spectrum when I changed the Bit Depth on Visual Analyser to 8

[Matt]

I'll give it a try later today.

-Matt

[Matt]

Ignore my last post. I noticed that I got about the same results whether the ends were hooked to anything or not. Turns out that I had the wrong audio channel, and there was still an earbud attached to it. The above chart was influenced by the noise in the room. I chopped off the earbud and switched channels, and now I have a good signal.

So, here's what I see coming into pin 4 on the PIC... what's your take on it?

-Matt

[RavingLunatic]

Check your diodes, it looks like you are getting a positive and negative AC cycle.

Are both D1 and D2 wired up correctly?

Is your D3 getting AC on it's cathode?

Double/triple check how your diodes are hooked up in comparison with the Ren-T design.

Edit: I noticed that the current Ren-T schematic in the wiki is from the XB proto version and doesn't show how a center-tap transformer hooks up. I made a drawing of how the ZC is done on the current Ren-T with a center-tap transformer.

[Matt]

The diodes are wired correctly. My Ren-T is wired to the schematic in Wayne J's post.

I did another test on my Line In port this time and got this...looking better but still not a clean digital signal. Those spikes in the positive direction seem to flash up and down while the analyser is on.

I'll actually have some time tomorrow to test what the serial data or clock look like to confirm the workings of the scope.

Thoughts?
-Matt

[ErnieHorning]

Matt, it looks like its working fine to me. Now check the output of Q1; this is the square pin. It should look similar except it will be inverted.