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Timer for 1.5v motor

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JaDogg1000

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Okay guys I am a complete ignoramus when it comes to electronic circuits. I can wire a bathroom. However when you start talking resister, mosfet, cap, pot and all these things my mind goes numb. But I have this project that I really desire to finish and I need some real help. I sure wish I had an electronic geek friend to pick his brain but I don't. I found this forum and you guys seem to have way more knowledge about this stuff than I can imagine. I am trying real hard to start understanding this stuff, but just give it to me as plain as possible and I will try to not ask too many stupid questions.
Anyway here's my quandry.

I am building these bird decoys that will have spinning wings. The wings will be powered by these low draw motors that I would like to power from a 1.5vD battery and hopefully have it last a long time. The motors work fine with the 1.5v, but can handle more. I think they will last a month of continuous use on one D battery. Okay here's the tricky part. I would like to have these motors kick on for a short while then be off for a short while. Exact timing is not important but for reference lets say on for 30 sec/Off for 30 sec. Or even on for 20sec/ Off for 60 sec. I want to have a multiple of these so some are always coming on and some are going off. So far what I think I need is a multivibrator of some sort, but when I look at schematics of these all I see is Greek! Plus I don't have any idea what would work with my voltage requirements. Looking into the Multivibrator it seems that I could build an Astable and have it switch back and forth between two motors? then one circuit could be used on two of the birds?
So can anyone help me out? I would like to keep it as simple as possible. Thanks ahead of time.
 
You need to do your sums to find out how much power you can take from the battery. If you run 30s on / 30s off you will basically double the running time. 20s on / 60s off, where it is running 1/4 the time, means that you will get 4 times as long as running continuously.

I think you will find that a motor will only run for a few hours on a D cell, so if you want to have a month of use, you will only be able to run for a tiny fraction of the time. It's probably easiest to wire a motor up and let it kill the battery. I think you'll need a clock not a calendar to see how long it lasts.

Not many circuits will run from 1.5 V, and you need to remember that the battery voltage will fall to about 1.1 V when it is nearly dead. If your circuit stops at say 1.3 V you will only get about half the life out of the battery.
 
I don't need the thing to run for a month, thats just what the motor is supposed to do with no load on it. I would like it to just run for a day of use probably about 6hrs. I can up the battery if I have to. Its just that Ideally I would like to use a D cell per setup.
 
I have a really simple circuit for something like this but it needs higher voltage. Do you have any idea how much current the motors take? Maybe we could run them from a 9 volt battery and drop the voltage some.
 
The CMOS version of the 555 timer will run on 1.5 volts.
 
Here is a link to the motors specs. **broken link removed**

The motor I'm using is 14415. I appreciate any help on this. I am willing to learn, I just need some guidence.
 
Wings

Jason,

Attached is a schematic that should work for you. It occurs to me that you may want to run several birds off of one or 2 circuits. If that's so let me know and we can beef it up a bit.
 

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Real world....Vgs(th) for the 2n7002 is between 1V and 2.5V for an Id of only 250uA. And that's just the threshold, not the saturation Vgs. The Vds(on) can be as as high as 3V. I think you would better off driving an NPN transistor, with only a 3V supply.

Ken
 
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Wings II

Ken is right. The fet is marginal at this voltage. Here is an update with the transistor. Uses a little more current, but with the 2 batteries you have plenty i think. Two other things: Get the CMOS version of the 555 if you can. It uses a lot less current If you go to someplace like radio shack they will have both types. Also note the polarity of the 22 ufd. capacitor.
 

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Okay I got all the parts, except I couldn't get the CMOS as every store in the KC area is out of them and they couldn't tell me when the could get more. So i got the regular 555. I couldn't find the original transistor you recommended so I grabbed another that I thought might work. So I put it all together and all I got was a continuous running motor. I was a little confused as to which pin on the transistor went where, so I tried it in all the different positions. I tore it all apart and tried again but still no luck. So I thought maybe I would try a simpler circuit just to see if I was doing anything right at all. I tried the first astable circuit listed here **broken link removed** . I just used the parts I had and I got it to kick the motor on for about 15 secs, then off 15 secs. Is there any reason that this circuit won't work in the long run? I think I can live with the results of that unless you guys see something that will cause a problem in the future. Its a little cheaper too since I want to build a load of them.
 
Wings III

Here is an updated schematic with pin numbers etc. Switched back to the FET to save power. If you send me your e-mail I'll send you a link to the parts with price and data sheets. There is about a dollars worth of parts excluding the batteries.
 

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