Spin Semiconductor

Posted: **Fri Jun 30, 2017 6:39 am**

Background: I've got a momentary switch that bypasses POT0 to send the ref voltage and 'max' the pot for momentary weirdness.

Now, it might be the case that a) I'm making assumptions or b) I've made a hardware mistake, but for an example like this (generated from DL's SpinCAD) I find that if POT0 is turned fully counter-clockwise and I hit the momentary, I get a click, the 'clip' LED lights and the pedal returns to functioning only when I let go of the switch. Do I need to include a minimum value or an offset or something?

Alternatively is it something else that I'm not considering?

This only seems to happen on a couple of patches that I've written or generated, so I'm not 100% sure what the pattern is.

Code: Select all

; Pot 0: pitch of dry signal
; Pot 1: pitch of wet signal (-1/+1)
; Pot 2: mix of wet signal
; 
; 
; ----------------------------
;------ Input
;------ Pot 0
;------ Pitch Shift
SKP RUN ,1
WLDR 0, 25455, 4096
LDAX ADCL
WRA 0,0.0
RDAX POT0,0.7768249512
WRAX RMP0_RATE,0.0000000000
CHO RDA,2,REG | COMPC,0
CHO RDA,2,0,1
WRA 4097,0.0
CHO RDA,2,COMPC | RPTR2,0
CHO RDA,2,RPTR2,1
CHO SOF,2,COMPC | NA,0.0
CHO RDA,2,NA,4097
WRAX REG0,0.0000000000
;------ Pot 1
;------ Pot 2
;------ Pitch Shift
SKP RUN ,1
WLDR 1, 8192, 4096
LDAX ADCL
WRA 4099,0.0
RDAX POT1,1.0000000000
SOF 1.0000000000,-0.5000000000
SKP GEZ,1
SOF 0.5000000000,0.0000000000
WRAX RMP1_RATE,0.0000000000
CHO RDA,3,REG | COMPC,4099
CHO RDA,3,0,4100
WRA 8196,0.0
CHO RDA,3,COMPC | RPTR2,4099
CHO RDA,3,RPTR2,4100
CHO SOF,3,COMPC | NA,0.0
CHO RDA,3,NA,8196
WRAX REG1,0.0000000000
;------ Mixer 2:1
RDAX REG0,1.0000000000
WRAX REG2,0.0000000000
RDAX REG1,1.0000000000
MULX POT2
RDAX REG2,1.0000000000
WRAX REG2,0.0000000000
;------ Output
RDAX REG2,1.0000000000
WRAX DACL,0.0000000000

Posted: **Fri Jun 30, 2017 7:41 am**

Post the schematic of the pot and switch. Surely you're making a short circuit when you press the switch and the pot is maxed

Posted: **Fri Jun 30, 2017 8:57 am**

I'm assuming you have one leg of the switch connected to power, the other connected to the pot input. When you have the pot turned all the way down you are essentially connecting the pot input to ground, and when you hit the switch you are connecting power to the pot input which is connected to ground shorting out the circuit.

Posted: **Fri Jun 30, 2017 12:06 pm**

+1 ^ maybe show a diagram of how you have the switch and pot wired then it will be easier to figure out the problem.

Posted: **Mon Jul 10, 2017 4:06 am**

Hey guys, at work but I will check the schematic when I get home... I took out a few parts to save space on this iteration and maybe I did something stupid like taking out a resistor... that's a good point (and would be par for the course in terms of rookie bloody errors I suppose). Thanks for the help!

Posted: **Thu Jul 13, 2017 12:40 am**

Yeah, so the momentary is effectively tying the wiper (pin 2) and pin 3 of POT0 together, where pin 1 is to GND.

So I can see why that's shorting - my question is, when the wiper is over at the ground side, what's the best way of stopping this happening? Presumably adding a small value of resistor between pin 1 and GND? I guess the issue there is that it will mean a minimum value at all times...

Actually wait, surely a cap between GND and pin1 is the way to go? Because then you're just never going to directly link VREF and GND when you hit the momentary.

Posted: **Thu Jul 13, 2017 10:14 am**

I've done this be putting 2 resistors in series between the wiper of the pot and the pot input on the FV-1. One side of the momentary switch then goes to the junction of the two resistors and the other side to 3.3 Volts. This stops the switch shorting out the pot but doesn't affect normal operation.

It's resistors R17 and R18 on this schematic http://www.aronnelson.com/gallery/main. ... ewsIndex=1

Posted: **Fri Jul 14, 2017 8:31 am**

Ah, that's clever. I guess I'd have to go with some tiny value though as otherwise it would cause the pitch to be noticeably higher than the dry signal...

Posted: **Wed Jul 19, 2017 12:30 pm**

the_frey wrote:Ah, that's clever. I guess I'd have to go with some tiny value though as otherwise it would cause the pitch to be noticeably higher than the dry signal...

Compensate the offset in the soft

Posted: **Thu Jul 20, 2017 4:27 am**

Ah, yes, good point. I should have more coffee before I reply, haha.

Spin Semiconductor

Glitch/power off at minimum pot value?

Glitch/power off at minimum pot value?