Power distribution (total beginner)

Community General Discussions
1

Hi folks,

After years of thinking about it I've finally started to build my first bot. I know next to nothing about electronics and microcontrollers so I have a steep learning curve ahead!

I started my project by buying a kit - the Dagu Rover 5 '2WD' kit . I'm planning on coupling this with a Raspberry Pi and some other bits and bobs. In brief, the way I'm dreaming it is that the RaPi will be the 'brains', which in turn controls the Arduino (Red Back Spider), which in turn controls the motors of the Rover 5 ... 

Which leads me to my first question - how to power everything? The motors seem straight forward enough - attach battery pack to the correct terminals on the motor controller and the job is done. However that still leaves me needing 5v for the motor controller logic, 7V - 32V for the Red Back Spider, 5v for the RaPi and probably 5v 3A for a USB hub (WiFi, webcam, etc). Having two power packs seems logical to me - one for the motors and another for the 'brains' - but I'm really not sure how to handle the disperate voltage requirments etc.

TIA

Huw

 

 

 

2

You might be able to get

You might be able to get away with powering the Arduino through the Ras-Pi, and using one pack combined.

Battery Pack 1 -> Ras-Pi -> Arduino -> Sensors, etc

Battery Pack 2 -> Motor Controller -> Motors, Servos, etc

You would power the motor controller logic through the arduino 5v logic.

 

Here’s an analogy that might help: You have a soda cup with a straw.

Voltage = size of the straw. The bigger the straw, the stronger the flow of ‘juice’ you’ll pump.

Current = size of the cup. The bigger the cup, the more ‘juice’ you’ll have available to pump.

 

I believe this is correct, if it’s not I hope someone smarter than myself will come along and correct me :slight_smile: Hope it helps!

3

Missing post?

Am I the only one who can’t see my last post? Strange …

4

**Apologies **

Apologies for creating confusion. Oddbot is right - I bought the Robosavvy kit “DAGU Rover 5 Kit 2WD with 2 Optical Encoders.

Arduino MEGA + DC Motor Controller with Encoder support”.

My logic behind two batteries was that the motors are likely to use power quicker than the other kit - and the RasPi probably won’t like dropping voltages etc. However I will bow to your experience and design with one power source in mind.

>> The Redback Spider controller has a DC-DC converter built in that can deliver 5V @ 3A

I guess this is the way to go then - use the Redback Spider to power the motor controller and the RasPi. It’s probably got enough juice for the USB hub too so long as I don’t add too much stuff to it.

Thanks :slight_smile:

 

5

A friend has offered me a 6v

A friend has offered me a 6v sealed lead acid battery and charger for free. Apart from weight (around 500g ish) are there any disadvantages to using something like this compared to the 7.2V NiMh or 7.4V LiPo batteries mentioned by OddBot?

6

Apart size and weight?

Apart size and weight? None…

But, still on “weight” subject, NiMh and LiPo offers much more capacity “per gram”.

A heavier robot has more friction, higher comsuption… etc etc. Lead acid batteries may be a good choice for bigger robots.