I need a 25-30 cm long leadscrew for my project. It is going to move a small wagon with one end of the 2 part dustcover.
Acme leadscrew was very expensive on ebay and other sources. The ones i found was often from indusrtial hardware suppliers for people with large budgets.
So for now im just going to use a threaded rod and a nut. But that would require a lot of turns to move the wagon 25cm.
Do anyone have any tips on where i can find something like this? i have thought about old printers but i think they mostly use steppermotors and some kind of belt.
Problem 2
In a guide(see bottom) they wire up a button with a resistor, it that really necessary? cant I just run one wire to 5V then up to the button and then down to a digital pin?
3
Would it be safe to take 12V from my computer and feed it into a H-bridge L293H? or should i get a separate wall plug for it? Im mostly concerned about the large amps ~40A destroying everything.
Cannot provide any info on leadscrew .... hopefully, other members will be able to do so.
Problem 2: In a guide(see bottom) they wire up a button with a resistor, it that really necessary? cant I just run one wire to 5V then up to the button and then down to a digital pin?
The resistor is for safety reasons in case a short happens on the way to the Arduino... like maybe when I'm using my voltmeter probe and short two pins! It happens. As the input impedance on the digital input is very high, the resistor really has no significant voltage drop.
3: Would it be safe to take 12V from my computer and feed it into a H-bridge L293H? or should i get a separate wall plug for it? I'm mostly concerned about the large amps ~40A destroying everything.
Personally, even if I were drunk, I would not do this! This is a very dangerous way to secure 12V. Buy a nice lab supply with current limiting for your bench ( I use a 0 - 40V with max 2A ) for such things. When you go to project with this, consider the end-game supply; wall powered, battery powered, etc.
The whole project is going to sit on my computer, thats why it would be nice if i could use the 12 in the PC already. But i am assuming i will be able to power the arduino directly from the computer? As said it really will only drive some buttons and a H-bridge.
i will be able to power the arduino directly from the computer? As said it really will only drive some buttons and a H-bridge.
The good news is that all recent PCs can supply at least 500mA of current on the USB port. Most will simply shut-down until the overload is removed if the amount is exceeded; however, I have never tested such claims on any of my own hardware... but, in theory.
If you want to do the 12V thing cheap, you could use a 12V gelcell battery. I keep one around the bench for such things and use an old trickle charger to keep it happy.
On the mechanical side, I don't know of any direct alternative to a leadscrew. If you are just moving a light dust cover I might try building a chain or timing belt driven system with the Actobotics plastic timing chain and belt hardware sold by www.servocity.com and recently added to www.sparkfun.com as well. I have used it before and it is relatively cheap.
There may be another reason for the resistor you saw in the schematic. When the button is pushed in your case the digital pin would go to 5V, but where does it go when the button is unconnected? In this case you would need a pull down resistor from the digital pin to GND to make sure that the pin goes low when the button is not pressed. The Arduino does have built in pull up resistors that you can use, but in that case you would need to connect your button to GND instead of 5V.
for stepper motors, you can use a second power supply from a PC. these should not be expensive. just remember you have to short out the pin that is looking for connection to a computer.
as for the dust cover. you could take a piece of plastic pipe and cut it to make a cover. dust will fall down before it falls up.
the diameter of the screw was not mentioned. the larger the screw, the less threads per CM and the more it will move per revolution.
buy ACME threaded rod, not too expensive. then with a file, file the end to make your own tap. then tap threads into a plastic block. very low cost.
if you need FAST movement, then use a belt drive. you can get these from old printers, or order a timing belt. google cnc timing belt and you should get pictures of what others have done.
Where can i find ACME threaded rod? I searched ebay but it cost like 50 usd.
As for the half pipe to cathc dust, that was clever, i had not thought about that!
The speed is not that important as i start the computer and open the dust cover and then use it for 5+ hours.
The motor i bought is 6V 30RPM, i estimated a full rotation of the rod would be about one milimeter.
300/30=10 10 minutes to fully open it. so i have looked at another motor that is 12V 500RPM meaning it would take only ~40 seconds.
I don't want to spend too much considering its most for fun and i needed to buy alot of other stuff so this can function.
here in the US, a company called ENCO sells ACME screws. these are not high precision leadscrews, but thousands of home hobbyiests have used them in their CNC machines.
There should be some hardware supplier that sells them for much less than a lead screw.
If you are only trying to cover a fan outlet an old tray from a cd-drive might suffice. That is if you have one gathering dust so to say. I have taken apart two from an old computer and the drive for the tray seems in both cases like easy to control. There are even switches in place to sense the endplaces.
Sadly, it would cost to much to get the ENCO products to Sweden. I have also been thinking about some kind of spiral or rigid metal spring, there the wagon would move quite far every turn.
Why not use a simple method? A chain drive is proven technology. Two sprockets, one driven and the other idling, move the chain, Photocells detect the end of travel points. Or you could use a timing belt. Discarded printers will often have good stuff. I would prefer a belt or chain to a screw thread.
Edit: Forgot to mention... you definitely do not need a resistor. you wire your button or switch between GND and the pin, then use pinMode(pinNumber, INPUT_PULLUP);
This will use the internal pullup resistor, so your pin will not "float". The active state of the pin is then LOW.
