Phase 2 - LDR’s - Photoresistors

[Jer]

Hello pedalpcb community,

I would greatly appreciate some insight.

I am building the Phase ii.

Phase II - PedalPCB.com

Compare to Mu-Tron Phasor II

www.pedalpcb.com

It calls for KE-10720 LDR Photoresitors and a Yellow LD. I ordered all the parts per specifications in the build document but tayda was out of KE-10720.

So i ordered Photo Conductive Cell Resistor LDR 540nm RADIAL 5528.

From other threads i have gathered that the important details are the photo resistance and dark resistance which are very similar (good, i think). I have compared the manufacturing specs on both.

PR 10k to 20k. DR 0.5 M

There is some variation on rise and fall but the one that has me concerned is spectral peak.

KE-10720’s are 550 nm min to 650 nm max

https://www.taydaelectronics.com/datasheets/files/A-5795.PDF

The ones i ordered are 540 nm peak spectral value.

https://www.taydaelectronics.com/datasheets/files/A-1528-2.pdf

I note the specs are not totally aligned on how the specify that.

From what i gather 540 nm is a wavelength in the range of green. 650 nm is yellow.

I think the intent of the build is to match the sensor to the colour. What i am unsure of are other implications of swapping.


So here’s what i see my options are:
1. 3mm Yellow light with 540 nm LDRs
2. 5mm Green light with 540 nm LDRs
3. Order LDR’s from mouser for $20 + $30 shipping and get divorced.

I like my wife. I think option 2 is the way to go. And rely on the trim pots to dial it in.

I humbly request someone who understands this stuff to tell me the best approach. I dont want to go through all the effort of building this to cheap out and have it not sound good and sit on shelf instead of my board.

i have 5 mm green LED’s and 3 mm yellows. Does it matter for the lamp if its 3mm or 5 mm? I can get LED’s easy enough if it matters.

Please help. Thank you,
Jer

 

[Synchrony Pedalworks]

Your logic for option #2 seems correct. If it fails, swap the yellow LED. That should be an easy part exchange. I would do that prior ordering the expensive Mouser parts.

You could also socket the LED and try both with little risk of damaging the PCB

 

[Jer]

Your logic for option #2 seems correct. If it fails, swap the yellow LED. That should be an easy part exchange. I would do that prior ordering the expensive Mouser parts.

You could also socket the LED and try both with little risk of damaging the PCB

Thank you and maximum respect to your build page. I’ll report back on how it turns out upon receiving the parts and getting it built.

 

[Synchrony Pedalworks]

Thank you and maximum respect to your build page. I’ll report back on how it turns out upon receiving the parts and getting it built.

Ha! Thanks for the compliment! Please us know if you get it working with the green LED and LDRs. That will help others that run into a similar issue.

 

[Chuck D. Bones]

Don't be too concerned about the spectral peak. Getting enough light onto the LDR at any wavelength is not a problem. LDRs are very sensitive and a small amount of light is all you need. Yellow and green are both good choices, but red and orange would also work. Blue and white could work, but they are usually too bright. Use a diffused LED and DO NOT use a superbright.

 

[Jer]

@Chuck D. Bones
Thank you, good advice on “diffused”. I have green diffused and super bright that weren’t clearly labeled as such that i might have used. Lucky catch for me. Cheers.

Stay tuned for results. (It will be awhile)

 

[BrainDrain]

@Chuck D. Bones
Thank you, good advice on “diffused”. I have green diffused and super bright that weren’t clearly labeled as such that i might have used. Lucky catch for me. Cheers.

Stay tuned for results. (It will be awhile)

I’ve had good luck in the past with messaging Tayda about parts that are out of stock on their website. I usually just ask when they’ll be back in stock. A few times they updated the stock the same day. Might be worth a try.

 

[Jer]

Well folks. I have an issue but i dont think its related to my original questions. I believe the inside light is supposed to be oscillating and it’s not. I can adjust the brightness from off to full brightness with the trim pots. I have got power, true bypass (sort of) and sound when the the pedals engaged. It actually sounds kinda good but not “phasing”. I can make it phase manually with rate knob or waving it from dark to light with back plate off. I tryed swapping the charge pump for an LT1054 i had around with exact same result.

Its seems like its almost there.

Feedback and Rate dont seem to be doing much.

Weird thing. The lights on inside when its turned off.

Any advice here.

Am i just not doing something obvious with the trim pots?

I dont think i have solder bridges.




Thank you

 

[jwin615]

Try adjusting trim 2 and make sure you test with the lid/baseplate on.

 

[Jer]

Try adjusting trim 2 and make sure you test with the lid/baseplate on.

Is that 1k marked “102”?

I understand the LDR’s will function differently in the dark but will the light also act differently? Maybe thats where i am going wrong. I thought i should be able to observe the pulsating with lid off but that LDR’s would only pick it up when its closed.

 

[jwin615]

Is that 1k marked “102”?

I understand the LDR’s will function differently in the dark but will the light also act differently? Maybe thats where i am going wrong. I thought i should be able to observe the pulsating with lid off but that LDR’s would only pick it up when its closed.

Yes. You should be trying both though
See the excellent madbean phase 2 build doc, bottom of page 8 for an explanation of what the trimmers are for

https://madbeanpedals.com/projects/_folders/FilterMod/pdf/Glasshole24.pdf

As far as the lid goes, that's moreso once you get it pulsing, be sure to audio test it with the LDRs in the dark. Otherwise it's gonna react different.
Or, as in the madbean doc, figure out some sort of light shield.

 

[Chuck D. Bones]

Do you have a DMM?
We need to troubleshoot the LFO and LED driver. First, do like jwin615 suggested and see if you can get the trimpots dialed-in.
If that doesn't work out, we can use the DMM to assess the LFO and LED driver state of health.

When you say "The lights on inside when its turned off." do you mean when the pedal is in bypass mode? If so, that is normal. If you mean the LED is on when no power is applied, then DM me, I have a business proposition for you.

 

[Jer]

The abridged version of the solution: one Crappy TL 72. (It was a war to figure out and i mostly got lucky)

Gentleman, i dont think this thing working is just a phase. We got it.

Appreciate your support, your clues got me looking at the circuit diagram and using my brain. I usually just paint by numbers.

Can confirm the alternate
LDRs and a green LED work.

Thank you,