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neb



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# 208774 27-Feb-2017 11:38
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I've got an electronic pet feeder that I use if I have to go away for a couple of days to avoid having to keep asking the neighbours to come over and feed the cat. Problem is that for the last few weeks it's been failing with an error code each time it dispenses food, it grinds out food for about 15s (rather than dispensing a single portion) and then stops with an error display (just "E", there's no info). Hitting any key on the keypad resets it, so there's no actual error, it's a problem with the control electronics.

 

 

On the theory of many eyes possibly making bugs shallow, I thought I'd post some details here in case there's something I missed. Here's a shot of the internals:

 

 

 

 

The black round thing is the motor that drives the feed mechanism, which works fine. Below it an IR photoelectric sensor for, presumably, detecting blockages. I've removed the cover on that on the theory that it might be gummed up with something and mis-reporting a blockage, but it's all clear.

 

 

Expected behaviour: Release 1 portion of food.

 

 

Actual behaviour: Run for a full 15s (8 portions), then stop with an error code until you hit a key, at which point it returns to normal

 

 

Any ideas?

 

 

And as an extension, has anyone ever managed to build a basic electronic pet feeder that actually works? If you look at the reviews of the ones on Amazon, every single one has endless complaints about it jamming or not providing feed, making it pretty much useless for its intended purpose.

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neb



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  # 1727005 27-Feb-2017 11:44
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Interesting additional point: If I interrupt the beam while it's grinding out food, it stops instantly without an error code. So it's not a malfunctioning sensor as far as I can tell.

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  # 1727007 27-Feb-2017 11:46
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Does it use a timer chip to determine what constitutes a portion? Maybe that is faulty and it is just running until some safety mechanism kicks in. Whatever kind of feedback it uses to decide when a portion has been dispensed is clearly faulting. That is where you have to look.

 

 

 

 





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neb



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  # 1727056 27-Feb-2017 12:23
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Well, I may have found the problem. This photo will be useful for the explanation that follows:

 

 

 

 

It looks like the problem lies in the microswitch that it uses to detect feed being dispensed. This is pulsed four times every complete revolution of the (geared-down) motor. If I manually short out the switch contacts it stops after one portion, otherwise it keeps grinding out feed. So probably faulty microswitch.

 


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Vocus

  # 1727076 27-Feb-2017 13:05
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neb:  So probably faulty microswitch.

 

Yes that may well be it, easy and cheap fix.  To confirm, check the continuity across the switch while you actuate it.  

 

If you have some kind of contact cleaner (not something so heavy as 5:56 / wd-40 preferably but they may work at a pinch) squirt some in the switch and actuate it a few times see if it comes good.  You might still want to replace it but it may give you a few weeks for the parts to arrive.


neb



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  # 1727091 27-Feb-2017 13:15
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It worse'n that. Switch is fine, the problem seems to be that it's level-triggered rather than edge-triggered, so if the cam starts in a position where the switch is open then it never seems to sense, or react to, a close event. In the photo it's closed because I'd been rotating it manually to check for the clicks, if it starts in the open position it exhibits the fault. So the process of trying to diagnose the problem seems to have fixed it. Which is a pain, if it was a dodgy switch then I could replace it, but this seems to be a design flaw in the device as a whole where it doesn't count switch open/closings but relies on it starting in a fixed position and then returning to that.

 

 

... testiculos sobre un fuego grande...

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Vocus

  # 1727096 27-Feb-2017 13:18
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Time to put your own microcontroller in :D


neb



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  # 1727098 27-Feb-2017 13:24
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Or just design my own feeder. Every single feeder on Amazon with any number of reviews has complaints about it jamming, up to ones costing hundreds of dollars. Whoever can collar a mechanical engineer or two to design a feed mechanism that doesn't suck could make a mint on a feeder that actually works.

 

 

In any case it looks like the fix, if it happens again, would be to turn the feed screw by hand until the microswitch clicks. I'll have to run it for a week or two to see how it goes.

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Vocus

  # 1727107 27-Feb-2017 13:58
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A feed screw / auger should be pretty reliable, provided the motor has the required torque.  You could probably use a wood pellet feeder as a basis for one if you want something robust.


neb



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  # 1727125 27-Feb-2017 14:36
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Yeah, I thought about kludging something up using a pellet feed screw, but you end up having to do a lot of design work to get it right and work the bugs out. This one has actually had some thought put into it, e.g. the blockage-detecting sensor and revolution counter for the motor rather than just applying power for x seconds and hoping it worked, they just got the design wrong for the counter. There was a kickstartered one done a few years ago where they tried to Do It Right, and even that is showing up lots of problems (it's one of the Amazon-reviewed ones) now that it's been in use for awhile. Just did a search and there are two more lined up. I bet after 6-12 months they'll have lots of complaints as well as they start failing.

 

 

Edited to add: Another one, on Indiegogo, has already failed, the comments section is full of demands for refunds due to non-shipment, it was supposed to be ready two years ago. The two kickstartered ones are still at the "got my product, it keeps crashing/failing" stage, in other words the early adopters are the alpha testers.

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