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TOPIC: Hacking my new SafePet Rotating Litter Box for Cats

Hacking my new SafePet Rotating Litter Box for Cats 2 months 5 days ago #18035

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Greets All (JON) :)

I want to hack our new SafePet rotating littler box. In short, the motors on it run off of 25 volts AC and I want to switch them on and off. I got me some SSR modules that do 25vac to 220vac switching using a 3.3vdc signal. I do not have a heatsink on them because they are so freaking big! And the power adapter is rated for 650ma max. No I have not tested them yet to see if they get hot, even with less than an amp of power.

SO since some here (JON) are great with analog, I thought maybe you might have some other ideas about switch AC at 25vac to those motors, and maybe 120vac (USA) to a ceiling ventilation fan. These SSR's are cool, but with the heat sink, they are not exactly sporty.

Thanks as always for your time!

Hacking my new SafePet Rotating Litter Box for Cats 1 month 4 weeks ago #18036

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Well I looked up some circuits and the problem here with me is that since I am dealing with AC, even though it is not high levels, I need something solid I do not have to worry about. So I will go with the SSR for now (closely monitored for heat) for my AC motor switching needs. It is rated at 40 amps and I am dealing with a little over half an amp, so it should not present a heat problem. I am mounting it in an aluminum case anyway.

I'm using my successful bonding of an ESP8266 with an STM32F103 via usart. The ESP8266 is configured as a wireless telnet to the STM32. This allows me to send and receive data wireless to the STM32 via python scripts on one of my home servers running Debian Linux.

More as I do it. It's pretty simple stuff, CLI on the wireless telnet serial, a PIR sensor, some timer stuff, and the signal to the SSR.

Hacking my new SafePet Rotating Litter Box for Cats 1 month 1 week ago #18037

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Sorry for the late reply. I suspect you've done this by now, and I'm sure you don't have any troubles! I don't think you need a heat sink on thosd SSR bricks even when switching several amps.

I put a heatsink on the one I'm using to switch 1200 watts for our sous vide cooker. I don't think it even gets warm to the touch.
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Hacking my new SafePet Rotating Litter Box for Cats 2 weeks 6 days ago #18038

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Yes I went ahead and ordered heat sinks but did all sorts of testing. I placed a DS18B20 one-wire temperature sensor on both the heat sink and the SSR without the heat sink and tried different AC loads and voltages. I do not have that test data at the moment, but it was clear that the motors were not drawing nearly enough current to warrant a heat sink HOWEVER, when something went wrong with the cat box, the current shot up considerably and so did the heat. The motors that were jammed got awfully hot also. I fixed that issue in code. I have a question about that John now that I think of it... at the bottom...

I plan to post more about this wonderful enhancement for my cat box, when I get time, which seems to be exceedingly difficult these days.

My question... are AC motors reversible by changing the AC connection? I know that sounds like a dumb question, but one wire is neutral and one is hot, correct? And if not, does the wire connections matter? Reason for my question... when there is a jam, I want to reverse the process for a small period of time, like reverse the tracks, and then go forward again to see if the jam is released.

I also wonder... why AC geared motors? Are they more efficient than DC? Are they cheaper? Seem like a lot of people are replacing the motors on these things, most likely due to jams and overheating and then burnout.

THANK YOU JON for the reply!!! I was worried!!

Hacking my new SafePet Rotating Litter Box for Cats 2 weeks 4 days ago #18042

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Probably not (easily) possible to change the rotation of an electric motor. A geared DC motor would definitely be an advantage to deal with jams. It would also make it simple to monitor current with a power monitor chip like an INA 219 power monitor. You'd just need to size the shunt resistor to handle the maximum current range. When the current spiked at a stall (or leading up to a stall), you could reverse rotation to clear the jam.


Sorry I've not been around here much. I do have a few things to write about once I get some (paid) projects beaten into submission.

I have been answering some posts at Electrotech, but I think that's about to end. There are too many members of the "old boys club" who are quite certain they know more than anybody and everybody else and indeed, that anyone else replying to posts is an idiot. That's bad enough but the heavy-handed moderators ignore their little tirades while slapping down anyone who responds in kind.

Hacking my new SafePet Rotating Litter Box for Cats 2 weeks 4 days ago #18044

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That is unfortunate to hear, about Electrotech. I certainly understand what it is like when simple people that barely did any research work and want all the answers handed to them, but it really is important for people to be comfortable enough to ask silly questions. It is how they learn, it is just abused and needs more tolerance today than ever before.

There are a number of forums that suffer from both sides of that issue. People asking for instructions to people that are unwilling to help new people step into this wonderful world we are drawn to.

All I can say is that I am forever grateful to you and others who USE to be here, for tolerating my floods of ideas and silly uneducated questions. I sir have learned a LOT from everyone's patience and contributions, especially yours.

PS - I was hoping you would let me off the hook about my transistor question about the two lines that float above ground by 6 or more volts DC. Thing is, I have massed such a giant arsenal of devices, parts, and test equipment (giant in size for me that is), that I can certainly work out that issue on my own. I just do not take those dirt roads down rabbit holes so much because time is finite and I want (and need) to produce something useful knowing what I already know. Programming and adaptation are my strong skill sets. I just want to know everything else too.
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