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Driving 36volt motors from a 6volt controller

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DeathBlade

Sun May 14 2006, 03:48AM

Registered Member #300 Joined: Thu Mar 09 2006, 08:21PM
Location: pittsburgh,pa
Posts: 6

Well I was given this old industrial robot cart from a friend while is motors and body were rusted out the ultrasonic control unit is still salvageable from was I could see of the unit there were two drive motors that were 6 volt. The controller board used two wires fore each motor to control a second board which was integrated with the motors (there boards were water logged and destroyed) now I have these two 36volt wheel chair motor, and four relays.
From the original control board I checked the control wires and they put our 5volts each, so I connected the control board to a set of small motors and they responded to the input from the remote. But 5 volts wont drive 36volt motors, so I thought us this diagram do you think this would work, (I know the diagram is horrible )

[Edit: Go gere

to learn how to post pictures.]

...

Sun May 14 2006, 04:26AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Your diagram seems close, but not quite.
You need to wire each of the fixxed contacts of the relays to + and -, while the moving contact needs to go to the motor. Try redrawing the schematic with the relays opened/closed and you will see what I mean.

btw, you might want to resize that pic before a mod does...

DeathBlade

Tue May 30 2006, 01:57AM

Registered Member #300 Joined: Thu Mar 09 2006, 08:21PM
Location: pittsburgh,pa
Posts: 6

Well I found that the 5volts from the control module could not trigger the relays I had so I used some 5volt coil reed relays and they literly melted, so I got out the relays I used origanly and though to control the 12volts for the coils for the relays with a RCA3055 transistor for each relay. Here is the latest diagram, in this the yellow wires from the control unit can be either positive or negative, also I was able to break open one of the old motors though the motors control relays were water logged and the motors rusted to peices I was able to see that the original control was almost exactly like the first diagram.

1148953476 300 FT1630 Diagram2

...

Tue May 30 2006, 02:33AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

You should add a resistor in series with the base of the transistors. The value is not critical, try 300ohms for now, it the transistors seem to get hot reduce the value. Also, add a diode across the the coil of the relay to prevent the back emf from blowing out your circuit. You also might want to put a diode in series with the base of the transistor (I am not sure how npn's take reverse voltage on the base). Finally, you need to hook the 12v source so that the - connects to the transistor's ground, and the + goes to both coils of the relays. You also need to make sure that the ground of the whole mess is connected to the ground of the controller.

Bjørn

Tue May 30 2006, 02:58AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

It is not going to work like the diagram shows and adding 300 Ohms in series with the transistor will make sure that the relays will never work no matter how they are wired. I know what ... meant but it is not really what he wrote,

This thread is not good enough, you are asking us to design the whole circuit for you. Try to look up H-Bridge in google and the HvWiki and come back when you have a some specific questions.

DeathBlade

Thu Jun 08 2006, 09:11PM

Registered Member #300 Joined: Thu Mar 09 2006, 08:21PM
Location: pittsburgh,pa
Posts: 6

Well I have beaten this circuit, I found I couldn't drive the transistors from the the unknown chip that was connected to the original output control leads. So I broke out the some methylene chloride and etched away a large portion of the epoxy the was covering the circuit board and the carved away the last bits with a exacto knife and found the chips that drove the original motors where a set of LB1630 an sanyo motor control IC (though in the data sheet they were 20 pin chips, and the ones on the board a eight) I was able to dig the epoxy away and solder new leads onto the logic input pins of the chip and then to the relay transistors (PP3681). Though I had to drop the motor voltage to accommodate the transistors, because the transistors I had would not have been able to handle the 36 volts only being rated for 28volts, But the coils on the my first set of relays only activate a around 32 volts

So I had to find some others I found some relays with contacts rated a 30v dc a 3amps vs my previous one which were 60v dc at 25 amps, I'm wondering if new relays can handle a set of 12volt 70ah batteries in series.

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