Handy Motor

Handy Motor

Postby modorney » Mon Jan 02, 2017 3:27 pm

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Re: Handy Motor

Postby AstroGoat760 » Mon Jan 02, 2017 3:53 pm

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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Re: Handy Motor

Postby krokodil » Mon Jan 02, 2017 4:42 pm

AstroGoat760 wrote:Those should be good for small units like Galloping Geese and the like, so much as an appropriate resistor is used.



The resistor is not a best practice. It will change 12-4=8 V into heat. Also the motor working characteristic will heavily change and can happen that the model will not start in gradient.
It will be not an easy task to reduce the track voltage for such small motor.
Similar drive mechanizms are used in Bush Feldbahn (H0f) models. The track voltage is about 4,5V
It is my TT layout with the Bush NG train.

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Re: Handy Motor

Postby Bernd » Mon Jan 02, 2017 6:47 pm

I wonder of a 7805 voltage regulator would work?

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Re: Handy Motor

Postby krokodil » Tue Jan 03, 2017 2:56 am

Bernd wrote:I wonder of a 7805 voltage regulator would work?

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Depends how do you plan to use it.
Installed into the model in a 12V DC system, the model speed will rise almost linearly up to 6-8V in the tracks and stay constant over this voltage. The heat problem remains the same as with resistors. You will need two 7805 one for each direction and two diodes.
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Re: Handy Motor

Postby Bernd » Tue Jan 03, 2017 10:33 am

krokodil wrote:
Bernd wrote:I wonder of a 7805 voltage regulator would work?

Bernd


Depends how do you plan to use it.
Installed into the model in a 12V DC system, the model speed will rise almost linearly up to 6-8V in the tracks and stay constant over this voltage. The heat problem remains the same as with resistors. You will need two 7805 one for each direction and two diodes.


Ah, forgot about the reverse. I use a 5 volt regulator on board the engine, but I'm using radio control to the motor. Keep forgetting you guys use DCC or just plain DC. I have no heat build up in my 5 volt regulator. It takes the constant voltage from the track, 12 volts in my situation. Steps it down to 5 volts on the engine which the Receiver uses. The motor is 6 volt motor.

Here's my setup on a 2-6-0 HO scale engine.

The motor:

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The R/C receiver Rx41d-5v-W and voltage regulator:

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Deltang Receivers/Transmitters are now made in 12 to 14 volt versions.

Link to vendor: http://deltang.co.uk/

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Re: Handy Motor

Postby CN-TT » Tue Jan 03, 2017 11:58 am

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.
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Re: Handy Motor

Postby modorney » Wed Jan 04, 2017 2:53 pm

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.
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Re: Handy Motor

Postby krokodil » Wed Jan 04, 2017 3:18 pm

The problem will be ( as always. :-) ) that the MAX will start to work only after certain track voltage ( cca >5V)

I think a bit easier solution will be to use an enhanced FET (http://pdf1.alldatasheet.com/datasheet- ... asheet.pdf) or similar device and a small potentiometer for each direction. With 2 of these elements and 2 diodes you can setup the voltage divider ( about 1 to 4) ie 4 V track voltage change will generate 1 Volt change on the motor.
I did not test yet ( I need to get some FETs). For both directions you will need 2 FETs, 2 trimmers and 2 diodes
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Re: Handy Motor

Postby Bernd » Wed Jan 04, 2017 6:58 pm

I'm starting to think it would be better to throw the motor away and get a 12 volt motor to use those gears on. It would be easier and simpler. Just my opinion.

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