switching polarity from + to - multiple times per second

Discussion in 'The Projects Forum' started by brandofryeman33@yahoo.com, Jan 7, 2011.

1. brandofryeman33@yahoo.com Thread Starter New Member

Jan 6, 2011
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0
Hey, my names brandon and im working on this project but i seemed to have run into a problem. Im trying to make a circuit to switch polarity multiple times a second. i want a motor to switch from positive to negitave and be able to control how many times a second it switches polarity. and also if possible i would like to be able to control the voltage as well. The project is not real big so i wouldnt want my circuit to be real big. Im not sure if this circuit would be possible but i hope someone could help me. I called a electrician and he told me i was crazy. Please help me. does anyone think that it could be done? '
need the voltage to vary from 1.5volts to -1.5 volts. Also would like to be able to change it to what i need like: 1.5 volts to 0 volts to -.75 voltsand back to 1.5. I want to switch polarity multiple times a second. and be able to choose specific voltage/polarity at any given interval.

2. CDRIVE Senior Member

Jul 1, 2008
2,223
99
If you switch the motor polarity multiple times a second the motor is just going to sit there a buzzzzzzz. What are you trying to do?

3. brandofryeman33@yahoo.com Thread Starter New Member

Jan 6, 2011
7
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i didnt mean to say motor. I just need something like say a rod about 2 inches long and maybe 1/4 inch diameter, like a nail to switch polarity. One side negitave and one side positive at all times unless its neutral. thats all I want, so when one side is positive the other is negative. i want to be able to control how many times a second it switches polarity and control the voltage. i want the voltage to max out at 1.5 volts. and -1.5 volts. is this possible?

4. thatoneguy AAC Fanatic!

Feb 19, 2009
6,357
718
Is this something along the lines of the "levitating ball" projects, where the coil is energized to keep the item from falling out when held vertically?

The reason I ask is there may be a simpler solution to your problem, or a more complex one.

5. blueroomelectronics AAC Fanatic!

Jul 22, 2007
1,758
98
What's it for? Your 2"x0.25" iron rod will need a fair amount of energy to move it back and forth at several times a second. At 1.5V no chance.
Why not do something like this.

6. CDRIVE Senior Member

Jul 1, 2008
2,223
99
Actually, this sounds more like the typical electromechanical 'Etcher' that was used as a high school shop project, back when they actually had shop.

7. brandofryeman33@yahoo.com Thread Starter New Member

Jan 6, 2011
7
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just say i have a C battery, with a wire on each side. also i have a pencil lying on the desk. i want to hook the c battery leads to each end of the pencil. I dont want it to move, just want to be able to switch polarity and voltage and be able to control how much voltage it has, and how many times a second it switches polarity.

Dec 26, 2010
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It would help to know what you are really trying to do. You seem to be reluctant to explain this, and we are left to guess whether this would be safe. For instance, a pencil could get very hot with a fairly small voltage applied to its graphite "lead".

9. brandofryeman33@yahoo.com Thread Starter New Member

Jan 6, 2011
7
0
just say i have a C battery, with a wire on each side. also i have a pencil lying on the desk. i want to hook the c battery leads to each end of the pencil. I dont want it to move, just want to be able to switch polarity and voltage and be able to control how much voltage it has, and how many times a second it switches polarity.

im just working on a school project. I know that im not the best explaining what i need. I just want somethimething (pos on one end and neg on the other) it doesnt matter what material its made from. I want to control the amount of voltage and the amount of times per second it switches polarity/voltage. i just wanted to experiment with different voltages and at different times during a second.

10. brandofryeman33@yahoo.com Thread Starter New Member

Jan 6, 2011
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.25 sec .50 sec .75 sec 1 sec
1.5v -1.5v 1.5v -1.5v
l l l l l l l l
l l l l l l l l
l l l l l l l l
l l l l l l l l
l l l l l l l l
-.75v .75v -.75v .75v

i want to experiment and put in whatever voltage i want at whatever part of a sec i want

.25 sec .50 sec .75 sec 1 sec
1v -.75v 1v -1.5v
l l l l l l l l
l l l l l l l l
l l l l l l l l
l l l l l l l l
l l l l l l l l
-.5v 1.5v -.5v .75v

11. brandofryeman33@yahoo.com Thread Starter New Member

Jan 6, 2011
7
0
i was trying to draw straight lines but they got bundled up, just picture a line from top to bottom

12. CDRIVE Senior Member

Jul 1, 2008
2,223
99
What's the point? A graphite pencil is passive, like a carbon resistor. Changing polarity won't change a thing. Evasion is an art form and should be left to professionals.

13. Kermit2 AAC Fanatic!

Feb 5, 2010
3,772
931

This will switch polarity for you as fast as you can push the switch.

10-15 changes per second should be possible if you use a momentary switch, a toggle switch would be much slower.

Time for some pencil torture

Tell it you won't stop till it writes you a check.

Dec 26, 2010
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Let's hope this IS nothing worse than a pointless exercise involving pencils or iron rods.

Looking back on some ill-advised things I did with electricity as a youth, I count myself very lucky to have survived. This makes me cautious about giving practical advice, particularly to young people.

Last edited: Jan 8, 2011
15. beenthere Retired Moderator

Apr 20, 2004
15,815
282
Perhaps the OP can state the purpose of this polarity switching? It begins to sound like a shocker.

16. CDRIVE Senior Member

Jul 1, 2008
2,223
99
When a poster is evasive it usually means his project falls into one of these categories.
(1) Nefarious and verboten on AAC.
(2) Automotive related and not permitted on AAC.
(3) Free electricity schemes.
(4) Wireless electricity schemes.
(5) The OP thinks he's got an idea for the habitual postings of 'Perpetual Motion Machines'.
(6) The OP thinks has invented something (conceptually) that's going to make him rich, despite not having any electronics skills.

Numbers 3 through 6 fall into the category of... "I must be evasive, because if I divulge what I'm doing it'll be stolen from me"!

EDIT: Come to think of it, I'd rather have our 'yutes' messing with 2 through 6 than spending there entire lives playing video games and watching sports, instead of playing sports. This includes adults too!

Last edited: Jan 8, 2011
17. brandofryeman33@yahoo.com Thread Starter New Member

Jan 6, 2011
7
0
thanks kermit 2, is there any way to make a momentary switch for that and be able to switch polarity like thousands of times or millions of times per second? I really need something like that, but switch polarity very very fast. thanks for your help everyone...

18. Kermit2 AAC Fanatic!

Feb 5, 2010
3,772
931
Thousands and millions of times a second is not what you indicated in your earlier posts. You said "you" wanted to control it.

An oscillator and transistor switch arrangement are possible, but at anything more than 50-100 times a second, relays are useless. They can't switch fast enough.

Tell us exactly what you need. What range of switching frequencies do you want.

If you say everything from 1 Hz to Milions of Hz, then you can wait for someone elses help. THAT is not a simple project for shocking pencils with.