Automatic Litterbox Central

I have no ampermeter. I was copying the other guy so I could be sure of success and not have to measure. I thought I got the same LED and resistor he got. Radio Shack only appears to have one LED that is 20mA (with 5V or 12V). Mine is red and 12VDC like his.

But yes the package says built in resistor and I didn't remove it. I think it's too hard for me to remove it. So next I should try to find another LED. Probably need to order it online. I prefer a different color too, and a brighter one if possible.

100 ohm is the lowest 1/4 watt resistor they have at Radio Shack. Maybe I can try it with no in-line resistor? Because of the built-in resistor.

The LED package says Forward (supply) voltage is 12.0 VDCmax so I think it will work if I remove the other resistor? But still, this LED says only 1.5 mcd It looks ok when I view it, but probably other LEDs would be much brighter.

Removed the resistor and tried it. Worked in tech mode but didn't dispense water in 4+3 mode.

I ordered a much brighter LED. It has a built in resistor too but is made for 12V. I really hope the new LED works.

kittymom wrote:Removed the resistor and tried it. Worked in tech mode but didn't dispense water in 4+3 mode.

I ordered a much brighter LED. It has a built in resistor too but is made for 12V. I really hope the new LED works.

If there is a built-in resistor, you don't need extra resistor. Connect Power Supply directly to the led.

The brighter LED seems to work. It successfully did the 4+3 cycle (drain, fill, drain, dry). I will try a full cycle soon, surely it will work. I just hope it continues working for a long time. I need to solder the wires and post photos.

It's much brighter. I didn't get the brightest available but it's brighter than normal. I'm glad I didn't get even brighter, so it's not lighting up the room much. I got white.

(The RadioShack LED was not bright enough. RadioShack was unnecessary since they had no power supply, only had a low brightness LED, and the resistor was not needed since it's built into the LEDs I bought.)

The full cycle ran fine.

I'm considering cutting another water sensor and buying another power supply, since I already have another LED and now I know what I'm doing.

Wonder if rcb4t2 has had any problems with his? Can this have problem if the sensor gets dirty/scratched? I am assuming yes, but that it's much less likely to have problems.

One thing I dislike is normally I can interchange my 60 and 120 processors, but now I won't be able to without turning around the sensor/LED. However, if it's functioning and not giving me problems, then I don't need to interchange them much.

It ran 2 more times successfully.

Here is a photo with the rim off. Sorry, you can't see much. I put electrical tape to block the light, since I didn't do the eraser in the same way.

Thanks again.

Glad to see you got your modified liquid sensor working! Do you have a list of components and part numbers for your final configuration?

BruceInKC wrote:Glad to see you got your modified liquid sensor working! Do you have a list of components and part numbers for your final configuration?

I ended up with a prewired bright 20mA LED with built-in resistor, saves some steps. So, it just needed connecting to the 12V power supply which I already had on hand. I have seen the same power supply on Amazon, and I got my LED on eBay. It's probably available many other places too.

I used a small rectangular piece of eraser but I just stuck it in the middle, and squished the LED wires in, and put the electrical tape over top. Oh and duct tape on the back so the wires don't stick out.

The way I'm running the wires under the plastic rim isn't the best, but it works okay.

After working about 6 times, it's not working again. The LED is lit and in the same position (taped down), and I hadn't changed anything else, but I just tried a cycle and it ran dry. It wouldn't output water in tech mode either. I promptly removed the cut sensor and LED, and placed an original sensor, and it's running perfectly. The bottom of the cut sensor is dirty, however, I feel like it's dirty BECAUSE it ran a dry cycle. It's possible the sensor was dirty first, but this is bothersome.

Hey all - sorry I haven't checked back in until now.

My implementation still works fine, although it doesn't help the dirty sensor problem. Ultimately it still needs to be cleaned periodically. Using the solution from this thread bought me some time but I'm now going to look into the Darlington pair solution with the screws. Good luck to all!

rcb4t2 wrote:Hey all - sorry I haven't checked back in until now.

My implementation still works fine, although it doesn't help the dirty sensor problem. Ultimately it still needs to be cleaned periodically. Using the solution from this thread bought me some time but I'm now going to look into the Darlington pair solution with the screws. Good luck to all!

What LED model do you use? Do you know its chracteristics?
I use the solution in two CG. The first one needs to be clean once in 3 month. The second one need to be clean once a week. I've ordered new LED for second CG (L1503SRCF Kingbright 5V/20Ma/4000mCd instead of noname).
5V LED needs 470 Ohm resistor on 12V Power Supply.