How to reverse polarity digitally (with software) ?

I would like to get a DC motor to spin in one direction for a specific number of rotations and then spin in the opposite direction for the same amount of rotations and continue to do this automatically? I know that changing the direction of the motor is achieved by reversing the polarity from the power supply, but how can this be done without using a switch or potentiometer or any other piece of hardware? I am new to this stuff so any help is much appreciated. Thanks

Question by luch   |  last reply

how can i refill a mont blanc meisterstuck fountain pen?

I already have a refill ink available. I just need to know how to put the ink inside the pen. Thanks

Question by    |  last reply

How can I print my bookmarks in xp?

I want to print my bookmarks to move them to all my computers, so every computer has the same listings

Question by maruawe   |  last reply

How does one get their instructable to be "featured"? Answered

Just wondering, I was looking at some of the "featured" Instructables and some of them are brand new. What are the requirements that would qualify yours to become "featured"? Is it Views? Artistic merit? score? I'm curious! Thanks!

Question by poolgirlblue   |  last reply

can we make a self sustained solar robot? Answered

What we require for making a robot self sustained

Question by avi4u1988   |  last reply



Question by POWERFTK 

the distance of others planets measure with tausends of years of light speeds. Answered

How come a ufo creator on board reach to earht.are thair life too long to do it?

Question by tayyareci   |  last reply

how do i make a weak lead pencial staple shooter shoot harder ?

The way yall descirbe this is good but it shoots to soft

Question by  

Can you still add lights and inputs on an audrino board with the motor shield attached? Answered

I'm new to the audrino board but it looks to be a great piece of kit. I still don't fully understand the benefits of the motor shield. Is if just higher voltage motors, can you still add lights and input on an audrino board with the motor shield attached?

Question by funbob   |  last reply

how would i go about hooking an xbox 360 head set up to my corded home telephone?

Yeah i just think this would be kinda cool and iv been researchin but i can find anything all though i didnt look to hard any help would be apreciated the phone is so old that it has no speaker phone and id like to be able to use it hands free so any ideas the phone i have to work with is in the pic below

Question by Goomanhimer   |  last reply

What infomation are needed to calculate fps for an air canon? Answered

I know that fps is speed unit, and I'm trying to calculate the initial speed(or the power) for my air canon. Information I have: 1: value of the air chamber 2: psi 3: diameter of the barrel 4: length of the barrel 5: diameter of the air release valve will those information be enough? How to calculate fps or power from information above?

Question by    |  last reply

how can i wire my car to call my cellphone when my car alarm is going off?

I would like to wire an old cell phone to my car alam so that it will call my new cell when it is triggered i live in an aptmt building on th 18th floor so it it is inpossible th hear the siren .....if any one can help please let me know how

Question by alldemcarz   |  last reply

why wont my ibook turn on when pluged in but runs fine off battery?

Yeah my ibook recenly stopd working it run off battery but wont charge and wont run off the ac charger iv been through 3 new chargers

Question by Goomanhimer   |  last reply

can i use a motorola w325?

Can I use a flip phone?

Question by    |  last reply

How to get past the user page in windows xp

My friend was given a computer that had had xp a clean reinstall and does not know what to do to get past the user page. Can anyone help? Thanks

Question by    |  last reply

How does a processor work?

Question by    |  last reply

How Should I Partition My New 500GB Hard Drive With Windows XP Pro? Answered

I have a new 500Gb Hard Drive, and I'm going to install XP Pro on it. How should I partition my drive if I plan to have a lot of pictures, a lot of music, and games on it? Also, how big is XP Pro when it is fully installed? Thanks.

Question by Hoboman   |  last reply

where do i find a wireless transmitter for a camera? I.E. for a live web show

I dont want a mile of cord that somebody could trip over....

Question by conrad2468   |  last reply

Why did nobody video the plane crashing into the Hudson?

Wasn't it in a highly populated area?? Doesn't everybody carry camera phones these days??

Question by Slidin_sidewayz   |  last reply

how do you build a lcd flashlight with variable brightness?

How do you build a lcd flashlight with variable brightness?

Question by    |  last reply

How do I splice cables together?

How do I splice cables together?

Question by Zem   |  last reply

Small CNC Machine help?!! Answered

Looking into building a CNC maybe 15 x 20 inches working area, and need help:O Ive seen several instructables about it but still not sure which type of motors to use and why, where to buy the circuitboard OR how to program a DIY one, what are the 4th and 5th axes, and will it be expensive? Also are there any other hazards i should think about during the build? Any help would be greatly apprecited, thanks.

Question by brimckeon   |  last reply

who conceptualized

Who dunnit?

Question by gorgo333   |  last reply

LED power suppy help?

I am plan to run 4 leds in a seires parallel configuration. The leds have a forward voltage of 5.2 and run at 350 ma. Would it draw more power if I had a higher input voltage or would it still draw the same amout. I am trying to decide between lithium ion batteries and NMh.

Question by jack.h   |  last reply

Is Virtual PC Overclocking my processor?

Cpuz says that my processor is running at 830MHz maximum in virtual pc My processor speed is 800HMz my host os is windows XPSP3 and the os in virtual PC is windows 2000 Neptune(go figure) edition Also my physical computer says that my cpu is running at about 790MHz

Question by ReCreate   |  last reply

How do I make a noise-detecting traffic light?

I am not sure how many people have seen these, but they are used in Elementary school alot. Basically, when the light is green the noise level is at the right level, if it is yellow it is getting a bit too loud and red is WAY too loud. I want to use this type of idea in my classroom. It doesn't have to be a traffic light but a series of light. I just don't know much about wiring.

Question by MrFish7   |  last reply

how can I get the wireless I have at my house to pick up on my PSP? Answered

I have wireless at my house and my PSP can sense the signal, but for some odd reason I can't get it to connect!

Question by king_zilla   |  last reply

Can I replace a 3V watch type battery with two 1.5V AA batteries? Answered

I'm building an edge lit card like the one in the link, but in a frame. I have an LED that came with one of those LED "candles" but it's powered by a 3V watch battery. I want to use the LED and noise circuit, which makes the LED flicker, from the candle and attach it to a solar panel I got from an LED garden light and 2 AA batteries. Can I just hook it up to the LED or do I need a resistor? Shoud I hook it up in series or parallel? How should I hook up the solar panel to charge the batteries? It's similar to a sun jar principal. Thanks.

Question by bastion72   |  last reply

can pressure monitoring valves stems in a 2003 Cadillac Seville be replaced with standard valve stems?

Have ongoing problem of pressure stems leaking. have replaced two and they are expensive.

Question by    |  last reply

Can we use Electromagnetic waves to produce current. Like a cellphone starts charging when it recieves a call?

Its just an idea that struck me when i my cell phone's battery was dead due to a power cut. Can it be made possible. KINDLY DON"T PASS FUNNY REMARKS.

Question by Karan1   |  last reply

how do i change brakes for a 95 esscort?

I need instructions to change the brakes in a 95 esscort

Question by    |  last reply