Author Topic: Patrick, RAD v1.0 + Raspberry Pi + gadgets, build log and request for help  (Read 1747 times)

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Offline caramellcubeTopic starter

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First, thanks again for the information on where to find replacement screws for the RAD series. I have a load more questions for this project so I thought starting a build log thread would be better than posting them all seperately. This is just about the most complex project I've ever started so any advice, suggestions or ideas would be much appreciated.

Technical details

Patrick started off as a RAD v1.0 robot found at a car boot with no battery or controller. Some quick testing showed all the motors are still working fine, so my plan is to replace the head and driver board with a completely custom made unit, and add an 11.1v lipo battery for power. The head is partially based on an earlier project, a sensor-equipped timelapse camera, but this is intended to be more of a "do-anything robot", so the list of gadgets includes the following...

   Raspberry Pi 2
   Arduino Mega 2560
   NoIR camera fitted with a selectable IR-cut filter and CS-mount socket.
   TCS34725 RGB sensor
   PIR motion sensors
   MLX90614 non-contact thermometer
   SR-04 sonar ping sensor
   DHT-22 temperature and humidity sensor
   TGS2600 air quality sensor
   mosfet based electric charge detector
   Adafruit ultimate GPS reciever
   USB microphone
   IR LED illuminator
   12x neopixel ring light
   5mw laser
   5 inch HDMI display
   amplified speakers
   USB WiFi adapter
   7 port USB hub


1) Audio
The speakers should be able to play music for a group of people outdoors. I have a pair of 3 inch, 4 ohm, 5 watt speakers that are powerfull enough, and was going to wire them to an Adafruit 20w d-class amplifier board connected to the Raspberry Pi's audio out, the I2C bus for volume control, and the direct 11.1v feed from the LiPo for power. Is there a better way to handle the audio in terms of power to weight & size than this? All the 20w speakers I've found are too big for the head, but if I drive the 5w speakers, will I just have to software limit the volume to stop them blowing? I don't have the amplifier board yet but was going to go with it based on it's size and efficiency, and the fact that it can be put into standby mode when not in use.

2) Power management
I'm trying to make the 5AH battery last as long as possible by giving the Raspberry Pi the ability to turn off anything that's not in use, but I'm really not sure how to go about this. I was going to put a latching relay between the 5v output of the BEC and the input of the USB hub, controlled by 2 GPIO pins of the Pi (the arduino is powered by the hub, so this would shut down most of the gadgets for a soft sleep mode). The HDMI screen backlight is another large drain though, it has a tiny toggle switch for controlling the backlight that I might be able to solder to an optocoupler, or I could use another relay to control the 5v feed to it. The power supply so far uses 2 buck circuits, a BEC, and a MoPi board, so I'd like to avoid adding too much more complexity but I don't want it to waste too much power either. Any suggestions?

Those are the main points I'm having difficulty with so far. At the moment I'm just trying to design and print a stack of mounting plates to hold all the boards inside the head. Anyway, thanks in advance for any advice and I'll post back when there's some progress.


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