SammichSID Rotary Encoder Problem **FIXED**

MIDIbox SID
1

Hey guys,

Sorry in advance if this is answered elsewhere, but I looked around on the forum a bit and saw a few other people had bad encoders, but couldn’t see any more specific details to help with my particular problem so I’m posting a new thread.

So, I finished assembling my sammichSID last night and it all worked flawlessly the first time except for the rotary encoder, which I believe is dead to the world. No matter what screen I am on, nothing happens when I twiddle the encoder. Having looked at the manual it looks like the rotary encoder should flip through the screens and change values for selected items on the LCD.

I’ve beep-tested the encoder to make sure that my traces and soldering are good, and although the joints seem to be fine, I’m not sure if the results I am seeing are correct. From the control surface PCB, I see that the board will take one of two different rotary encoder sizes. The encoder I have has three prongs on the bottom with the wide spacing, one prong on each side, and no prongs on the top. Following the traces, I see that my encoder only seems to have two traces that connect with the resistor network above the 74HC16 on the bottom right of the control PCB on pins 2 & 3; if I had the other encoder type that the board is made for, it looks like a third trace would run down from the top left prong to the resistor network on pin 4.

When I beep-test my rotary encoder, all three prongs beep, but two prongs appear to be connected to the resistor network on pin 2 and one prong is connected to pin 3. I’m confused by the fact that the far right prong on the rotary encoder causes a beep on pin 2 of the resistor network since there are no traces connecting these two; the only answer I can think of is that my rotary encoder bridges the middle prong and the far right prong. None of the rotary encoder prongs appear to be connected to pin 4 on the resistor network.

I have attached a photo with color-coded blobs to show where the connections are registering. Note that my resistor network is soldered very close to the PCB so I tested the connections against the 74HC16 pins that are passed through to by the resistor network. I was hoping somebody could help me with the following questions:

  1. Are the connections the rotary encoder is making correct based on my tests?

  2. Assuming they are correct, is it possible that my rotary encoder is bad? Is there any other testing I should do before I de-solder it?

  3. Are there any further troubleshooting steps that are recommended in this situation?

Thanks in advance for any assistance. I’m super excited to get this issue resolved and start playing with my sammichSID!

  • max
    post-7724-060755900 1292822239_thumb.png
2

Picture the rotary encoder like two switches with a common pin. The common pin is pin 3, which is connected to ground. Pins 1 and 2 connect to the 74HC165. As the encoder turns, it closes each of the two switches in sequence, thus you can detect which direction the encoder is being turned by the “pulses”. See here for more technical explanations: http://www.midibox.org/dokuwiki/doku.php?id=encoders

So it’s normal for pin 1 and/or pin 2 to be connnected to pin 3, depending on the position of the shaft. You should do a continuity test between pin 1 and pin 3 while rotating the encoder, and listen for the beep going on and off. Repeat for between pin 2 and pin 3.

So to answer your questions:

  1. Yes, but test more as I describe above.

  2. You can’t rule out faulty encoder at this stage.

  3. Yes, see above. But also…

  • check orientation of the resistor networks

  • check no shorts between any of the IC pins

  • check encoder pins aren’t touching (and shorting with) the heatsink underneath

  • did you upload the setup_sammich_sid.hex file (and not another one)?

  • do the buttons work? Can you press 1st select button and get the Ensemble menu? Can you press Shift and get the Shift menu?

3

Thanks Wilba, I’ll run these tests today and will respond with my findings.

4

Thanks for the tip, Wilba. After you explained the way the encoder works, I ran the continuity test and found that pins 2 & 3 had constant continuity regardless of what was happening with the encoder knob, while pins 1 & 2 only beeped when I turned the knob. I flipped over the board and saw a little blob of solder on the connections for the smaller encoder (picture attached, blob outlined in blue). Since those connections are bridged with the ones for the larger encoder on the PCB, I had a constant connection between pins 2 & 3. I removed the solder and now it all works great.

Here comes a beer for you! :slight_smile:

Cheers,

5

ug glug glug

Thanks.

FYI the alternate pins are for encoders which I never use nor plan to ever use, but I can’t resist putting them in just in case someone wants them.

6

Dude, this thing sounds totally awesome - none of the demos I saw on YouTube did it any justice. Here’s some photos of the build.

http://www.flickr.com/photos/maximporges/sets/72157625643566528/

Cheers,

  • max