Getting ready for the service droid :)
November 19, 2013
So I've ordered the Dagu service droid :) http://letsmakerobots.com/node/38776
I'm getting the service droid with a Rover 5 (4 motors/encoders), 4 channel motor controller and Dagu Red Back Spider.
I already have a Rover 5 with 4 motors on which I use the 4 channel motor controller and Red Back Spider. I'm powering everything from a 2S Lipo (3000mAh). You can see it here: http://letsmakerobots.com/node/31410 or on my blog: http://www.bajdi.com/category/rover-5/
On my current Rover 5 the 2S Lipo feeds 3 devices:
- Motor controller
- Red Back Spider
- UBEC (powers the 4 servos of my gripper)
I also needed a separate 5V regulator to power the logic of the motor controller. You could use the 5V from the Red Back Spider but I prefer a separate regulator. If you power the motor controller and detach the 5V logic voltage you risk the chance of blowing it up. I destroyed one controller that way. I recommend you use the screw terminals to connect the logic voltage (and not the pins).
Another thing I needed was a 3V3 regulator for my wireless nRF24L01 modules (the Red back spider does not have a 3V3 vreg).
To accomplish the above things I soldered some terminals and 2 voltage regulators to a piece of perfboard. I later added a voltage divider to read the battery voltage, then I needed some transistors (for my "headlights") and so on... The board became a real mess after a while. I then started playing with Eagle and designed a small PCB for my Rover.
I started thinking about the service droid and what I would need to connect everything. The service droid comes with 8 servos. I think that's a bit to much for the 3A regulator on the Red back spider. I'm planning to add a Raspberry Pi + Camera (already have both), that also needs about 1A @ 5V (RPi+wifi+camera). I would prefer to power the RPi from the 5V on the Red Back Spider.
I've now come up with the following PCB to power and connect all the various devices on my service droid:
High resolution PCB: http://www.bajdi.com/wp-content/uploads/2013/11/Service-droid-PCB.png
High resolution schematic: http://www.bajdi.com/wp-content/uploads/2013/11/Service-droid-schematic.png
The board has 2 regulators. An LM1084 5A 5V low dropout linear regulator and a small low dropout LP2950 3V3 regulator. It has all the necessary pins and terminals to connect all the electronics. I chose those regulators because I have them in stock :) The servos will be powered with a 5 or 8A UBEC, since I have a bunch of spares from my hexapod projects :p
I would like to know what you guys think about it, any things I should add? And how you would power/connect all the electronics on a service droid / Rover 5.