Let's Make Robots!

motor driver idea

Hey all,

I'm trying to create a bot that uses a lot of forward/backward motor action, and I'm hoping to make a low-power, small, lightwieght motor control using switch transistors. However, my electronics experience is -5. I came up with this idea that seems simple and effective, but I'm sure there's something I don't understand about the process. So with that in mind, here's my ultra-simple H-bridge.

hbridgeIdea.gif

The idea is that both "A" transistor bases are connected to one outpin, ditto for both "B" transistors. Obviously, I'll need some resistance along the way. But could something this simple really work?

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cause neweby.....I Need Connector Simple Schema for Connector A and B for this Circuit Sir......

Please sent to my mail : peternaklayer@gmail.com

 

NOTE :

I will use at Egg Incubator....

- Motor Spec as same as power window motor in car

- This Circuit will be connect to Timer 3 Hours Intervals

- For Stop Motor, I will using microswitch (End Tray)

Regards,

Anwar

cause neweby.....I Need Connector Simple Schema for Connector A and B for this Circuit Sir......

Please sent to my mail : peternaklayer@gmail.com

 

NOTE :

I will use at Egg Incubator....

- Motor Spec as same as power window motor in car

- This Circuit will be connect to Timer 3 Hours Intervals

- For Stop Motor, I will using microswitch (End Tray)

Regards,

Anwar

Since you said that your knowledge of electronics is -5, I think the best to you it buy something already made. 

remeber you said  "low-power, small, lightwieght motor control using switch transistors" 

Or a Full Bridge like 298 or 293 (small motors).

look for some already made board at ebay.

 

So your answer to the question is "don't ask questions"? What's your follow up, "Google it?"

Might be a good idea to do a bit of a search, and see if anyone has got a working NPN over PNP or even NMOS over PMOS h-bridge out there. There are a number of schematics on the web, some working, some not, and even devices with a couple transistors manufactured together to make P over N devices, not the other way around. Generally PNPs are on the topside next to the supply they switch off of, and NPNs are near ground which they switch off of; just as P channels FETs are near positive and N-channel are near ground. Just sayin', may be fixing the switching problem in a wrong way.

Now by all means experiment if possible, and maybe there might be something new that hasn't been developed before. Might even be a pretty cool solution that does actually allow things to work better than has been thought of before.

The first setup i posted or the second one (same but with PNP at the bottom) should work fine if, instead of BJTs we used FETs right? With p-channels substituting the PNPs and n-channels substituting the NPNs. There would be no shorting since the gate of the MOSFET is isolated from the source and drain.

Below is a simple H bridge using bi-polar transistors. Two additional NPN transistors have been added for voltage traslation so that the motors can be driven by a higher voltage than the control logic voltage. Depending on transistors used and motor drive voltage, the resistor values may need adjustment but this should be fine for 6V-15V motors being driven by logic circuits running on 3V-6V. Click on image for a larger picture.

Bi-polar_H_bridge__small__Schematic.jpg

I'v recommend using a BD681 for the NPN and BD682 for the PNP. They can handle a maximum of 4A. These are darlington transistors which actually need about 1.3V from base to emmiter to turn on but have a higher gain (750 hfe) so that only about 5mA is required to flow from base to emitter for saturation to occur with a 4A load. The voltage translation transistors can be any signal transistor. The BC548 is a commonly available type that is quite cheap.

cause neweby.....I Need Connector Simple Schema for Connector A and B for this Circuit (Output from Bi-polar H-Bridge) Sir......

Please sent to my mail : peternaklayer@gmail.com

 

NOTE :

I will use at Egg Incubator....

- Motor Spec as same as power window motor in car

- This Circuit will be connect to Timer 3 Hours Intervals

- For Stop Motor, I will using microswitch (End Tray)

Regards,

Anwar

Most of what I've seen in terms of H-Bridges, one always have current flowing into the motor in an crossed kinda way.

What, for me, makes no sense at all is that A is connected to the left side and B to the right. It would make sense that a would be connect to Upper-Left and Lower-Right and B inversely.

Can some-one please help me understand how this design works?

I just realised even this won't work very well because even if you change the 2K2 resistors to 100 ohms you will still have trouble saturating the transistors for a 4A load. Plus you'll drop at least 1.3V across each collector-emitter junction. This is why FETs were invented. Replace the 2K2 resistors with 100 ohms and it will be good for maybe 2A continuous.