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Dagu rover 5 power supply

Hi, I have already made the start here robot and I am now moving this idea onto the dagu rover 5 robot chassis. When I turn the robot on it moves very slowly I think this is because the motors are designed for 5-7 volts and the 3 AA baterries are just under 5 volts and that there are 4 motors to power. If I use the 6 AA battery holder that comes with the chassis I am guessing I will need to use resistors so that the sharpe IR sensor recieves the correct voltage and not way too much. However, I do not know where to conect the resistors on my picaxe 28 project board. I also dont know whether the resistor array that the start here robot instructions uses already solves this problem. 

If you have any advice I would be pleased to hear it.

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Bajdi's picture

You don't need a different mcu, you need a motor controller... Your picaxe will have no problem controlling a motor controller.

Okay, thank you very much for your help. I think i'll have a look at the motor controller that you previously mentioned. 

Thanks again

Bajdi's picture

Uh, a L293D can do 600mA max per channel. My Rover 5 at full tilt powered from a 2 cell Lipo draws about 0,8A per motor. So you are trying to pull 1,6A (2 motors) from a L293D that can only give 600mA ... When doing quick turns the motors draw more then 1A, when I remote control it and quickly shift from forward to backwards the current goes up to almost 2A per motor. You need a decent h-bridge chip to run a 4WD Rover 5. I use the Dagu 4 channel motor controller.

Thank you for the help, what microcontroller do you use? So am I write in saying my picaxe 28 project board cannot be used to controll my 4WD Dagu Rover 5?

 

OddBot's picture

To begin with, which Rover 5 chassis are you useing, the 2WD or 4WD?

You should use batteries that can deliver about 2A per motor so a 4WD chassis needs batteries that can deliver about 8A. Normally the motors should draw less than 1 amp on smooth flat ground but you need to assume worst case.

Only use LiPo, Li-Ion or NiMh batteries rated for at least 2600mAH. Alkaline batteries will curl up their toes and die in about 10 minutes if your lucky.

Your Sharp sensor should be powered by a regulated 5V supply. Forget using resistors to limit power unless you like buying new sensors every day or like sensors with extremely limited range. Consult Manual 3 for Picaxe.

Right, that sounds good. 

I am using the Rover 5 4WD version with encoders (but currently I am not using the encoders).

So if I use a LiPo, LI-Ion or NiMh battery rated for at least 2600mAH and attach them to the two power points i did for the 3 AA batteries should that be enough to power the motors? Also, if I use this method of powering the robot does that mean the voltage for the Sharpe sensor will be too much? In which case would I regulate the power just for the sensor?

Sorry if these are stupid questions but as you may have guessed, I am new to robotics.

OddBot's picture

Perhaps you should have started this forum with a full explanation of what hardware you are using. You Have now told us you have a 4WD Rover 5 chassis and metioned a picaxe 28 development board but how are you are you driving the motors?  The L293D on a picaxe board will shit itself and die before it can drive a Rover 5. Especially a 4WD version.

When ever you ask a question you should alway give us all the information. We cannot read your mind from the other side of the world.

Okay, sorry for any inconvenience, I didnt realise this might be more complicated than I originally thought. Here's all of the info:

I have essentially connected the two motors on the left hand side and the two motors on the right hand side with jumper cables and then connected the two left hand side motors into one of the motor ports and the other two motors into the other motor port on the picaxe 28 pin project board which is used in the start here robot.

I assumed that as this board with this setup could power the two motors on the start here robot it could manage this but am I wrong?