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Reverse polarity switch with delay for DC motor

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Moderator: pebe

Postby pebe » Fri Sep 17, 2010 1:27 pm

You could probably use a switched mode power supply, something like this, because their regulation is good.
http://www.ebuyer.com/product/190365?ut ... m=products
It would give you 2A at a range of voltages.

I could not suggest anything for you for a motor. There are so many variables that only you could decide, eg. physical size, voltage, fixing methods, drive methods, etc. Just look at the available bits from Maplins and RS, etc., or Google on Ebay.
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same circuit with a 9v motor

Postby chamindag » Sun Jan 30, 2011 6:57 am

Can i do the same circuit for a 9v motor. How can i go about doing that?
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Where's the diagram?

Postby JimiRo » Tue Mar 22, 2011 8:29 pm

Do you have a diagram for this, pebe? I've looked all over the net for this circuit for weeks now. Thought I finally found it, but no diagram or parts list! Can you help me out with these? I'm not that experienced with electronics, but I can build a model airplane and I can solder so I figured I would be able to build this circuit if I had a diagram and parts list. Being an artist, I'm a visual kinda guy, so I understand things better if I can see a diagram instead of just text. I can read circuit diagrams and know what most of the standard symbols mean. I'm building a light mover for a large vivarium, I have everything done but the electronics. I'd also like to incorporate this circuit into some kinetic sculptures.
Thanks in advance for the help.

Okay I did another google search and got this same post and now it has the gif available, don't know why it didn't let me see it the first time. Even after I registered and signed in, it still wouldn't show me anything but your text description. What's up with that, what do I need to do in the future to let me see such things if they aren't visible?

What type of relays do I need?
Thanks again.
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Postby pebe » Tue Mar 22, 2011 8:42 pm

Hi JimiRo,
Do you mean a circuit of the motor drive, or the switched mode power supply?
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Postby JimiRo » Wed Mar 23, 2011 6:29 pm

I was referring to the Rev. Polarity Motor Driver, but I was able to see the GIF after I came back to the site. I also wanted to make sure I got the right relays - my small 30 rpm gearmotor is 12V, not sure about the amps, but the other motors in the series were all 1 amp or less. I ordered it from a hobby site expecting to get an info sheet, but nothing came with it. When I consulted the Japanese manufacturer's web site, the motor wasn't listed, I'm assuming it had been discontinued.

I'm kinda new to building electronic devices, but I've been repairing mine and friends' musical electronic equipment for years, such as replacing blown resistors, caps, etc. and jumpers for cracked circuit boards, and even making simple distortion pedals for guitars, so I know my way around a soldering iron. Like a lot of artists, I have poor math skills, but I'm pretty good at designing and making mechanical devices, now I would like to develop some electronic skills. Any help would be greatly appreciated and let me know if I could help you with any graphic art.

PS - Along with the relay info could you suggest which switches would work best for this, I'll be getting most of my components from Radio Shack.
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Postby pebe » Thu Mar 24, 2011 1:48 pm

I've had a quick look at the Radio Shack site, but there doessn't seem to be much variety and specifications are a bit sparse.

Are there any alternative suppliers where you live? There may be a suitable supplier on the net.
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Postby JimiRo » Thu Mar 24, 2011 7:14 pm

They had the resistors, ICs, and diodes, I got all of those. They also had a lot of different relays and caps, as well. It's a small town Radio Shack that's been there 35 years, or more, they seem to carry more DIY circuit components than the newer ones in our malls. I already had a lot of left over switches - on/off, soft-touch on/off, and momentary ons. I assume all the switches are soft-touch on/offs. They didn't seem to have the 100uf, they had a 100pf, but I'm assuming that's too small. Ideally the motor would rest at the end of the track for 30 to 45 minutes, even an hour or so would be fine. I was planning on experimenting with different caps to see which would work best for my project, as long as I couldn't damage any of the other components with the wrong one. Can you give me an idea of which caps would be good for these times? Keep in mind I'm still learning the math and I haven't done any equations since high school Algebra, and I only just got by then. And what style relay should I get, remember my small 30 rpm gearmotor's 12v, don't know the Amps, but others in the series didn't go above 1 or 2 amps?

Thanks for taking the time to help.
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Postby pebe » Thu Mar 24, 2011 9:38 pm

I have looked again on Radio Shack's website and navigating round it is awful! They don't seem to know what a relay is, because after first telling me they had no stock, they presented me with a bunch of switches instead.

You can use any of their micro switches, or momentary push-to-on types. Use whatever looks easiest to fit.

I couldn't find a suitable relay there, but if you look round their shop you may have better luck. You are looking for two SPDT relays - that's Single Pole and Double Throw (2 way). They need to have 12V DC coils and have contacts rated at a minimum of 2Amps DC.

The capacitors specified are 100nF (nanofarads) - not 100uF (microfarads). 100nF = 0.1uF and they are readily available anywhere so Radio Shack should have plenty. If not, anything between 0.022uF and 1uF would do. 100pF is definitely too small.

The time spent at each end doesn't matter - it can be days if required. Just be sure the circuit is what you want, ie. when you apply power, the motor will run from one end to the other and stay there. Then you can switch off the power. When you re-apply power it will run in the reverse direction and again stop at the end. The process repeats every time you switch off then on again.
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Postby JimiRo » Fri Mar 25, 2011 4:30 pm

Okay I misunderstood what this circuit did. I thought it would go back and forth over and over, 24/7, until I chose to turn it off.

What I need is for a paludarium (terrarium with half land, half water to simulate a riverbank, with plants, reptiles and fish). Its 6 feet tall, 5 feet wide. Plants need more intense light than flourescents can provide, so I'm using a HID lamp, and instead of having two lamps, one on each side, I'll use a light mover to convey the lamp back and forth on a track, all day long. I would like it to pause around 15 to 30 minutes on each end before going the other way, because the largest plants are on each side and they need to get the most intense light. Everything needs to be automatic. The lamp and mover will be on a timer so they come on at 8 am and go off at 10 pm.

I'm attaching a diagram of the quickest way that I thought would work, but I didn't realize the timer I had with two output plug-ins turn off and on at the same time, not independently of each other. So I figured that I would have to build a circuit from scratch, which brought me to you.

Apologies for the confusion.

Can we modify your circuit to be automatic?
I guess I could use 2 of the Brinks' timers instead, but I was worried they would eventually fall out of sequence with each other. The instructions says they may lose or gain up to 2 minutes a month.
Last edited by JimiRo on Mon Mar 28, 2011 8:33 pm, edited 2 times in total.
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Postby JimiRo » Fri Mar 25, 2011 4:32 pm

I didn't mean for that jpeg to be so big, my jpeg is only 3.5"x3.5". Sorry I took up so much space. Why did it do that?
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Postby pebe » Fri Mar 25, 2011 8:44 pm

You don't need a jpeg file - they are great for photos but tend to have blurred edges on lines. A GIF file is much smaller, gives cleaner lines, and it can still handle primary colours. But you should have shrunk the drawing first using a photo program or similar, and then saved it as a GIF. For what it's worth, I draw circuits with the 'Paint' program that comes with Windows.

That circuit could be modified but it would need extra chips for timing - probably a 555 and a binary counter - plus extra caps and resistors, but it then starts to get big and messy.

A better way would be to replace all the ICs with a microcontroller. That would handle the motor direction switching and also the time delay between runs. A small 8pin PIC could be programmed to do it. The total component count would then be the PIC plus two switches, two relays, two transistors, two diodes, and a 5V regulator.

If you want to go that way and you are in no great hurry, I could program a PIC for you.
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Postby JimiRo » Mon Mar 28, 2011 7:03 pm

Hold off on the programming, but thanks for the offer, it's much appreciated. I'm going to give the Brinks Digital Timers and 2 separate power supplies a try. I mentioned in an earlier post that the dual one I have powers both the plug-ins at the same time, not independently of each other, like I assumed. I'm going to try two single output ones instead.
I used Corel Draw and exported it as a high resolution(500) JPEG. The original was only 3.5 inches by3.5 inches, I guess the high res was the problem. I'm a Graphic Artist, but I'm used to working with vector files(CDR and AI files) for garment screen printing and sign making. We do everything in-house so I rarely send files over the net. I occasionally send artwork proofs as high res JPEGs, but I didn't know that the actual size was effected by the resolution on some sites, or whatever. I'm sending a GIF with my original idea in case you didn't get the original (when I checked back later that day, it didn't show up at all).

Thanks again, it has been educational.
My Mover Diagram-2.gif
My Mover Diagram-2.gif (25.73 KiB) Viewed 89930 times
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Thermostat Controller

Postby heitjer » Thu Sep 22, 2011 3:01 am

Excellent Info - thanks!

I have a slightly different problem. I like to move a roof based on the temperature. I understand I can purchase a thermostat cheaply (http://www.youtube.com/watch?v=jnwJlApqoGc) that gives me 12V when temperature reaches trigger limit. It provides 12V until the temperature falls off below the lower limit.

Lets say 70deg should close the roof, 90 deg should open it. Initially when the temperature is below 90 there is no voltage out on the thermostat, anytime over 90 and all the way down to 70 we have 12V power.

Any thoughts?
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Postby miketaylor » Thu Sep 22, 2011 6:27 pm

I have seen some ideas fo light sensor only circuits, but am worried that during the summer months the door would open too ealy in the day/late at night. but very intelligent post.
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Re: Reverse polarity switch with delay for DC motor

Postby Pichammer » Mon Apr 30, 2012 12:34 am

Hi everyone , I know this post I rather old but as the subject related to a project I am doing I thought I would see if anyone is still around. I am doing a chicken door coop automatic door and using two relays to reverse polarity , I was want ing to use a pixace chip to tell the motor to run for X seconds when the timer comes on. Then at another predefined time the timer comes on and the chip tells the motor to close the door and run the motor for X seconds to close the door. The trouble is pic langue is new to me and I dont know where to start I am finding a little hard. Anyone ere can point men in the right direction Would be appreciated. Thank you
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