I'm an electronic retard

[Greggorio]

I have never bothered to learn about electronics. Well I've never needed to which has stuffed me as I am now lost in a world of resistors (that have stripes on them that mean something but I'm not that clued up on volts, watts, ohms and Amp's either), micro switches and ermmm other things.

Basically I've built a cabinet incubator from an old fridge. I have made a very basic egg turning mechanism based on this

**broken link removed**

the tray moves and the floor doesn't and this pulls the eggs along and the floor is made of something like rubber so it causes friction on the egg which means the egg rolls along. This is because an egg has to be turned a certain amount of times a day or the yolk or embryo can stick to the side of the shell and kill it.

Now this setup was made with bits of wire poking out either side of the incubator so you'd do it manually 4-5 times a day. What I want to do is run that wire as something a bit bendier into a pulley attached to the wall either side. The pulley will turn the wire 90 degress upwards. This will then run up through the floor above, where another shelf will be, and through another pulley and connect to that shelfs wire/string etc where it will then head up through the roof of the fridge. There will be then two more pulleys on the roof where both of these come through to turn them both 90 degrees again to meet each other in the middle of the top of the fridge.

(I thought it sensible to explain the whole process before i get to the electronics)
Now here is the bit that has stumped me. I want a motor that will run backwards and forwards at a low rpm and be connected to my wire that is connected to my pulleys and trays and so pull the trays one way and then back the other. Now the problem is I also need it to do it one way and then cut out for 30 mins to an hr and then go the other way.

So the motor needs to come on long enough to move the tray a limited distance. Now I can adjust some of that by gearing the motor upwards which would also lower the rpms but the rest of it is a bit beyond me.

I'm sorry if this doesn't make sense or is glaringly obvious or something.

Thanks in advance

 

[Diver300]

I think that you would be best with a stepper motor. They are good a going slowly, over a fixed distance. It is also easy to adjust the distance by adjusting the number of steps.

The downside is that you will be looking at using a microcontroller. Something like this MICROCHIP|DV164120|STARTER KIT, PICKIT 2 | Farnell United Kingdom will give you a programmer and a board with enough space for the additional components you'll need.

You can drive the stepper motor with 4 transistors. A 5 V stepper motor can be run from the same voltage as the microcontroller, but it will take more current than a higher voltage one.

If you use a normal brushed motor, it has the advantage that it will run when you just connect it to the supply, but you will need 4 transistors to reverse it, and you need something to time it forwards, something to time it in reverse, and something to time the gaps between movements. That will all add up to as much work as using a stepper motor, and the distance it goes will vary more.

 

[kchriste]

Assuming you can turn the eggs very slowly:
You could simply use a geared motor with a cam connected to a push rod to shuttle the egg tray back and forth. Something like a timer out of an old washing machine may work. No "electronics" needed if you can get a motor that is geared slow enough.

 

[Neal]

I like the cam and push rod idea. For the timer maybe you could use a timer that turns lights on and off at selectable intervals when you are on vacation. Some have holes for many selections for the on and off times.

 

[Hero999]

Just making a motor oscillate the assembly back and forth should be pretty straight forward. Four transistors could be used for the h-bridge and a bistable RS flip-flip (logic gates or a couple of transistors) with a couple of limit switches to provide the oscillation.

The timer to make it only operate five times a day is the only tricky part to do in hardware. If it's acceptable to keep it moving back and fourth 24/7 then this can be avoided but that might not be good for the eggs. You could avoid having to build your own timer by powering it from a timer plug.

How good are you at soldering and PCB work? Can you solder parts to a stripboard?

If you want to avoid a PCB you can probably replace the transistors with relays but it will be more expensive, bulky and will have a shorter lift because relays are mechanical components and will wear out.

You'll need to do some soldering or crimping to connect the wire to the motor and relays, just wrapping wire round terminals is not going to be very reliable.

It's probably a good idea to power the whole thing from a DC supply so you don't have to deal with mains voltages. You can buy wall plugs which convert the mains to a safe low voltage DC supply.

 

[Ubergeek63]

I think that you would be best with a stepper motor. They are good a going slowly, over a fixed distance. It is also easy to adjust the distance by adjusting the number of steps.

The downside is that you will be looking at using a microcontroller. Something like this MICROCHIP|DV164120|STARTER KIT, PICKIT 2 | Farnell United Kingdom will give you a programmer and a board with enough space for the additional components you'll need.

not true at all... he can use a step/direction controller and simple limit switches to reverse the direction...

I do hate it when you guys over complicate things!

 

[Ubergeek63]

The timer to make it only operate five times a day is the only tricky part to do in hardware. If it's acceptable to keep it moving back and fourth 24/7 then this can be avoided but that might not be good for the eggs. You could avoid having to build your own timer by powering it from a timer plug.

again... step/direction stepper controller and limit switches... just add a counter to delay the motion after hitting the limit.

 

[Boncuk]

Oh gosh!

Never heard about leverage connected to a motor letting the load swing left and right?

There is absolutely no need for an H-bridge or something similar reversing the motor!

Use a grill drive with the appropriate leverage and let it spin day and night.

You'll probably create dancing chicken applying that method.

Boncuk

 

[Hero999]

Can a nube easily do that though?

again... step/direction stepper controller and limit switches... just add a counter to delay the motion after hitting the limit.

Please expand, bear in mind this is someone who doesn't know much about electronics.

 

[Ubergeek63]

Please expand, bear in mind this is someone who doesn't know much about electronics.

I know... if it is needed i can unless someone else fills in the details... as of now i am actually posting from work while the stupid FPGA compiler churns at my constant attempts to work around a compiler bug

 

[Hero999]

Boncuk,
You have a good idea but it might not be practical for him to rock the entire tray.

He's using string to pull it back and forth so he could use a similar mechanism to pull each string alternately.

 

[Mickster]

If the eggs don't suffer from constant movement, perhaps a similar setup to a vehicle wiper-linkage could work?

Obviously, the motor would have to be geared down/replaced, along with calculating the distance from the wiper arm spindles to get the correct amount of travel, but there's an almost-ready solution possibly waiting in a junkyard somewhere.....for very little outlay.