# LDR help



## Zduck (Jul 16, 2021)

Howdy, I ordered the Pitch Witch and the Pendulum Tremolo PCBs. The Pendulum calls for GL5516 LDRs and the Pitch Witch for a “1M LDR”.

I’m new to LDRs, how do they differ and labelled?

This is what my local shop carries for LDRs. Will any of them work for these two pedals? They mark them as a range eg. 20K-2M?






						Search
					






					leeselectronic.com
				



LDRs


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## zgrav (Jul 16, 2021)

If you have Amazon Prime you can get a good assortment of LDRs for $12 with prompt delivery without extra shipping charges.  This kit includes the GL5516s and probably includes one or more LDRs with 1M resistance.  You can google the datasheets for more info.






						XINGYHENG 175pcs 7Values 5mm Photoresistor Optoresistor Photo Light Sensitive Resistor Assortment Kit (GL5506 /GL5516 /GL5526 /GL5528 /GL5537 /GM5539 /GL5549) (LDR Photo Resistors Light-dependen): Amazon.com: Industrial & Scientific
					

XINGYHENG 175pcs 7Values 5mm Photoresistor Optoresistor Photo Light Sensitive Resistor Assortment Kit (GL5506 /GL5516 /GL5526 /GL5528 /GL5537 /GM5539 /GL5549) (LDR Photo Resistors Light-dependen): Amazon.com: Industrial & Scientific



					www.amazon.com


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## Feral Feline (Jul 17, 2021)

Photoresistor - Wikipedia
					






					en.wikipedia.org
				




Basically, ZDuck, you're looking for light and dark resistances. Get the datasheet for the GL5516 and check what the light and dark resistances are. Take that info to Lee's and ask them for the GL5516 or its equivalent with the same or close-enough values. Start growing your collection of datasheets...


LDR_______________ LIGHT RESISTANCE ________DARK RESISTANCE
KE-10720___________10k–20k_____________________0.5M (I got a few of these from Tayda)
9200________________10k–50k ____________________5M        (I could use these, but...)
9203_________________5k–20k ____________________20M        (These are what I really need!)
NSL-7532                                    
GL5539
GL5549
NSL7530
54C679
etc


For the Pitch Witch, none of the LDRs at Lee's are appropriate. You only need 1M dark; you could try the 1k-3M and if it doesn't work well enough for your build you might find use for it in another build. Datasheet that matches dark requirement appears to be GL5528, but double-check that yourself. Also...

Consider putting together a small order of your most-needed parts and pad the order with some other common things you'll wind up using eventually in other builds such as A100k pots; 10k, 47k, 100k, resistors, jacks etc. Then you can order from another Canadian-based distributor such as A-1, Active Tech (Calgary), Avnet, BC-Robotics (Nanaimo), BJ Electric (Edmonton), Digikey (ON), Mouser (ON), etc...

It's always great to support your local brick&mortar shop, but if they don't have what you need...


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## Zduck (Jul 17, 2021)

Feral Feline said:


> Photoresistor - Wikipedia
> 
> 
> 
> ...


They do have 5528s! I’ll start with that and see how it works, thanks for your input.


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## Feral Feline (Jul 17, 2021)

Great!

I missed the 5528 somehow... probably because they didn't list the dark resistance.

spec:
Light Resistance at 10 Lux (at 25°C)8􏰀20KΩ 
Dark Resistance at 0 Lux 1.0MΩ(min)
Max Voltage (at 25°C) 150
Rise time 20 mSec
Decay time 30 mSec


Pricey.
Nearly double what it costs from some of the other suppliers, but then when you factor in shipping and time it takes to arrive...

This might be of interest to you:


			https://www.mouser.ca/datasheet/2/737/photocells-932884.pdf


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## mdc (Jan 23, 2022)

This is a very old thread that I'm bumping, but I figured this info might be of use to someone in the future SO...
With regard to the pitch witch/pitch pirate dlx, I built one up last night and used a random aliexpress vactrol instead of an LED/LCR combo and it seems to work perfectly well. 

I used one of these:








						2.8US $ |10PCS/Lot  LCR0203   LCR 0203  DIP 4   Linear optocoupler   New original|Cable Tools|   - AliExpress
					

Smarter Shopping, Better Living!  Aliexpress.com




					www.aliexpress.com
				




I don't really have much faith in whatever might be on that datasheet so I'd just take it as a pass/fail binary situation and in this case it passed.


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