## Handy Motor

modorney
Posts: 181
Joined: Tue Mar 10, 2015 6:39 pm
Location: Near San Francisco

### Handy Motor

AstroGoat760
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Joined: Fri Jul 24, 2009 8:07 pm
Location: Bemidji, Minnesota, USA

### Re: Handy Motor

Those should be good for small units like Galloping Geese and the like, so much as an appropriate resistor is used.
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CN-TT
Posts: 382
Joined: Mon Mar 10, 2014 2:51 pm
Location: Germany

### Re: Handy Motor

I'm reducing the voltage for my remote couplers with some rectifiers in a series connection. Dropping the voltage between .5 and .7 Volt per rectifier.

modorney
Posts: 181
Joined: Tue Mar 10, 2015 6:39 pm
Location: Near San Francisco

### Re: Handy Motor

I poked around last night and looked at a company called Maxim, who has a long history of making switched power supply integrated circuits. Switching supplies mean less heat, which is better than resistors.

I found this chip for 4 bucks - MAX17245 - and it has an evaluation kit available.

Normally, these chips are used in circuits for a fixed output. In other words, they have a sense input, which is expecting about one volt. So you "program" the chip with a resistor voltage divider. Say you want 5 volts. Then you have a 40k resistor and a 10 k resistor. You apply the output to the top of the 40k, tap the junction of the 40 and 10 k resistors for the sense, and ground the bottom of the 10. The chip will keep the junction at 1 volts, which means the output stays 5 volts.

In my application, I would sample the input (0 to 12 volts), divide it by 3 (0 to 4 volts) to create a target voltage, and add the difference between the target voltage and output voltage to 1 volt (sense voltage) to regulate the output.

A nice theory, let's see if it works. Of course, I need a reversing relay, to flip everything over.

It won't go down to zero, but a diode in series with the motor will get me down to 0.3 volts. I'll build up a breadboard and load it with meters, and make a video. I know it sounds Greek, but watching it might make it clearer.

harmi
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### Re: Handy Motor

This topic is probably already resolved, but anyhow adding a comment - I used to be a big fan of 78XX power linear stabilizers until I found dx.com step down modules working with significantly smaller heat production (high frequency conversion). Although my expectations were not initially high, they really do what they are supposed to do and for very small cost. For example adjustable one http://www.dx.com/s/298894, you can find fixed output too. Of course, do not rely on mentioned current capability of 3A or similarly inflated parameters listed there, but voltage is OK and for small engines it should be sufficient.
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