Photo-Resistor at Home Depot!!

Photo-Resistors are going out of style globally; getting hard to source.

I got a 3-buck "dusk-dawn" night-light from Home Depot. I assumed the light sensor would be a diode of some sort. No, it's got the wiggly line and it even says "CDS" on the PCB.

In hasty testing I got 1k3 in dining room light, 7k in dimmed light. These things usually go way-high in total darkness, and I bet it goes well below 1k in brighter light (sun, or faced with an LED).

It's on legs, you can easily desolder it. The capsule is coated to keep damp out, though I would not trust it in the weather.

If you replace the photo-R with like a 1K resistor, you have an always-on night-light, which is perfectly reasonable considering power is insignificant. Oh: the listing says 1 Lumen but the package says 2 Lumens, and I am inclined to the later rating, though hardly any real difference.

https://www.homedepot.com/p/Westek-Satin-Nickel-Industrial-Cage-LED-Night-Light-NL-CAGE-N/305009795  --- this is $3.26; the "Satin Nickel finish" up-close is grey plastic.

https://www.homedepot.com/p/Westek-White-Industrial-Cage-LED-Night-Light-NL-CAGE-W/305009776  --- this appears to be the exact same thing in White but priced at $3.99 ??

Neither is "At my store" but can be delivered there free, or to my house allegedly "free shipping" in 9 days.

We don't need no stinkin badges (safety regulations).....

Yup I recall old solar driveway lamps using both LDR daylight on/off sensor and separate solar cell to charge battery... The modern (cheaper) versions use the voltage from the solar cell to decide when to turn light on/off.

I hot-rodded one of my two solar driveway lamps by adding a second solar panel (salvaged from a dead unit) in series to grab more charge from low light conditions. I also put two stock inductors in series for the switching lamp driver to reduce lamp current and a larger capacity nicad battery (600maH vs 300maH).  The modified lamp is just as bright as stock lamps (subjectively) and runs for several hours longer every night (objectively). It turns on later than the stock lamp by 15 minutes to half hour because of the higher voltage from two solar cells wired in series. 

I am waiting for something to fail but it has been working much better than the stock lamp for several months now.

I am suffering from some cognitive dissonance... I would prefer that both of my driveway lamps worked pretty much the same, but i don't want to discard the better performing DIY modified lamp. I have parts to modify a second lamp but not much motivation. My decision would be easier if it hurried up and failed, but it still keeps working better than stock.  :

JR

I was going to post that Radio Shack used to have a variety pack of photo resistors, but then I searched and it looks like they're still available online.
https://www.radioshack.com/products/cds-photresistors

kool... time for a radio shack opto-compressor project....  : : :  (might need a hipper name.)

JR

There are still lenty of photo resistors available from the usual sources:

https://uk.farnell.com/c/optoelectronics-displays/photo-light-dependent-resistors-ldr

Cheers

Ian

JohnRoberts said:

kool... time for a radio shack opto-compressor project....  : : :  (might need a hipper name.)

JR

Click to expand...

When I use the small Radio Shack perfboard with copper pads, I scrape off a couple letters so it reads Rad hack!

Noticed this at walmart
https://www.walmart.com/ip/Meridian-Great-Value-4-Pack-LED-Automatic-Night-Light/26135731?wmlspartner=wlpa&selectedSellerId=0&wl13=5201&adid=22222222227018067603&wl0=&wl1=g&wl2=c&wl3=40933179752&wl4=pla-78865182152&wl5=9004021&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=local&wl12=26135731&wl13=5201&veh=sem&gclid=EAIaIQobChMI-fz51Zrk4AIVK7azCh2wQwQuEAQYASABEgKIs_D_BwE

I read this thread last night , and opto compressors came to mind as well ,
Is their anything in the newer technologies replacing photo resistors of interest to the audio designer , is it fast response time were looking for or does the photo transistor lend itself to audio in a particular way ?

I picked up  a few industrial type optical relay  sensors from some old outdoor light fittings at work , theyll switch  the mains  on or off . seemed to good to throw away  but I hadnt figured out what I could do with them .

I have boxes of the old solar garden lights that stopped working ,usually moisture creeps in and eventually they die . light levels are so low here in winter often they dont get a chance to charge to any great degree, cell  voltage decays away and its game over . I liked the effect when they worked , but after they broke down I ended up feeling a bit ashamed of the waste they created
for the sake of vanity .I had planned to use a 12v SLA with a panel to light a wooden structure in the garden ,but its still one of those things on the to-do list .

Tubetec said:

I read this thread last night , and opto compressors came to mind as well ,
Is their anything in the newer technologies replacing photo resistors of interest to the audio designer , is it fast response time were looking for or does the photo transistor lend itself to audio in a particular way ?

I picked up  a few industrial type optical relay  sensors from some old outdoor light fittings at work , theyll switch  the mains  on or off . seemed to good to throw away  but I hadnt figured out what I could do with them .

I have boxes of the old solar garden lights that stopped working ,usually moisture creeps in and eventually they die . light levels are so low here in winter often they dont get a chance to charge to any great degree, cell  voltage decays away and its game over . I liked the effect when they worked , but after they broke down I ended up feeling a bit ashamed of the waste they created
for the sake of vanity .I had planned to use a 12v SLA with a panel to light a wooden structure in the garden ,but its still one of those things on the to-do list .

Click to expand...

The old solar lamps used separate LDR on/off sensors, modern ones just rely on the solar panel output .

JR

Hi John,
I had noticed a difference over the years alright ,they became an order of magnitude simpler .
I might try reusing some of the lantern heads but possibly wired to a seperate panel and battery ,
Is a led driver advisable , or could I wire a few in series from 12 volts dc?
Could I wire it so the internal solar panel auto switches the lights at dusk from a central supply ?

Tubetec said:

Hi John,
I had noticed a difference over the years alright ,they became an order of magnitude simpler .
I might try reusing some of the lantern heads but possibly wired to a seperate panel and battery ,
Is a led driver advisable , or could I wire a few in series from 12 volts dc?
Could I wire it so the internal solar panel auto switches the lights at dusk from a central supply ?

Click to expand...

I've had some nerd entertainment messing with my lamps over the last couple decades.

I have found data sheets on the WWW but they are not in english. It appears as simple as possible. One solar cell, one battery, one IC, one LED and one inductor.  My speculation (guess) is that the solar cell directly charges the battery through the IC to also serve as daytime detector. After dark, the IC turns into a switcher dumping discrete pulses of current into the LED to regulate brightness. The data sheet shows a table of different current for different inductors. 

I learned some about this circuit empirically with my different modifications.  Placing the two (I added one from a broken lamp) solar panels in parallel offered no noticeable improvement. Wiring the two solar panel in series did however make a difference. As I noted before the lamp turns on later at night, but did not run significantly later into the night.

Putting a second inductor in parallel no doubt increased the current but did not make it noticeably brighter. OTOH wiring the second inductor in series which logically reduced current did not reduce brightness. So the winning combination is solar cells in series and inductors in series. The modified lamp is brighter longer than stock.

I suspect this works because LED brightness is non linear with current/power.  I have been waiting for the higher voltage to tax the battery or IC but it has been working better than stock for months.  8)

You are talking about very modest power... driving the LEDs with current pulses seems most efficient.. Perhaps a common battery but hard to improve on the low cost simple design.

JR

And of course the surplus places have plenty:
https://www.goldmine-elec-products.com/products.asp?dept=1510

If you want a package that includes the LED (the genericized "Vactrol" name/trademark that was apparently never enforced), they got these too for 99 cents each.  I bought a a pack of 50 when they were on sale for 25 cents each:
https://www.goldmine-elec-products.com/products.asp?dept=1389

I may spend my retirement making opto-compressors and selling 'em for big bux, though I suspect there's a whole lot of unit-to-unit variation of these things.

benb said:

I may spend my retirement making opto-compressors and selling 'em for big bux, though I suspect there's a whole lot of unit-to-unit variation of these things.

Click to expand...

I measured the response of Silonex NSL5910 LDRs a few years ago. I bought about 40 and tried matching them and quantifying the attack/release times. I had a pretty complicated National Instruments setup to measure it. Then got some older cells and measured those (reddish element vs grey element). Wasn't simple and took some time, but was really interesting.
Then I finally built a LA2A with handmade cells. It sounds excellent, but even if I could sell it for 'big bux' it would work out to a pretty small $/hr...    ;D
Figuring out why 'legendary' equipment sounds great isn't simple,.  The devil is in the details

I think it would be really cool to measure out a selection of opto cells and have them selectable on the compressor. Instead of a single sound (LA2A) you'd have a selection, where it would have been measured out on the test bench to go from fast to slow or have other characteristics.
Or you combinations if they were on pushbuttons.
Would take a ton of time to develop and then everyone would just want to buy the straight up LA2A clone anyway  ;D

dmp said:

Figuring out why 'legendary' equipment sounds great isn't simple,.  The devil is in the details

I think it would be really cool to measure out a selection of opto cells and have them selectable on the compressor. Instead of a single sound (LA2A) you'd have a selection, where it would have been measured out on the test bench to go from fast to slow or have other characteristics.
Or you combinations if they were on pushbuttons.
Would take a ton of time to develop and then everyone would just want to buy the straight up LA2A clone anyway  ;D

Click to expand...

Many years ago I designed an test fixture and wrote an automated program for matching the Vactec ‘s for Avalon. It graded all of the cells into bins for Stereo matching. The programming was developed over weeks and lots of sample testing.
Duke.

Dec 1959 RCA Review "should" excite LA2a fans. Mostly about Photoconductors *and* Electroluminescence.
https://www.americanradiohistory.com/RCA_Review_Issue_Key.htm
https://www.americanradiohistory.com/ARCHIVE-RCA/RCA-Review/RCA-Review-1959-Dec.pdf  (9MB PDF)

However I did not find a lot to chew on. RCA's interest in photoconductors was all about TV camera tubes, a very different app. The Electroluminescence article covers a lot of "recipe spice" which isn't much use unless you make your own. Some graphs are insightful.