Let's Make Robots!

Mr. General

  • Component category:
Mr._General_4.bas16.45 KB
Tone.zip9.68 KB
Mr__General_ATmega8_Edge_Detect.zip3.23 KB
Mr__General_ATmega8_Object_Detect.zip3.25 KB
Mr_General_Nano.zip3.21 KB
Vendor's Description: 

Video: http://www.youtube.com/watch?v=7Ve318yVUdU

DAGU products support site: https://sites.google.com/site/daguproducts/

This kit has recently been upgraded to include a USB interface, programming cable and the ATmega8A processor with the Arduino bootloader. The Manual has been updated with wiring instructions and diagram as well as USB driver instructions and trouble shooting section.

An improved "Tone" library is included on the CD as well as being available here that allows the Tone command to function on the ATmega8 processors (thanks to Robot Freak and Brett Hagman).

Based on Bot 08M, Mr. General is designed around a breadboard and includes the universal sensor brackets designed here at LMR as well as my IR object tracker in the form of a compound eye.

The Picaxe code was written for the picaxe 28X1 processor. The first Arduino code was written for an Arduino Nano which has 8 analog inputs. The second Arduino code is for an Arduino with only 6 analog inputs. This version uses digital inputs for the corner sensors which gives them slightly less range.

An IR LED and phototransistor is mounted on each corner and can be used for edge detection or object detection depending on how you choose to mount them. When mounted for object detection they can also be used for swarm communication. These sensors have an analog output but can also be used with digital inputs.

Here are some videos using a picaxe 28X1 and here is a video from GuangZhou University using the compound eye and an arduino to solve a maze.

The compound eye allows your robot to track a moving object but can also be used for IR communication between two robots. Other range sensors could also be fitted to the sensor bracket.

2 factory modified, continuous rotation servos allow speed and direction of each wheel to be controlled by a single digital output.

The kit does not include a micro-controller as the breadboard allows a wide variety of processors to be used. A generous 140 piece cable pack allows easy connection between the breadboard and sensors.

2 individual voltage busses allow for up to 3 different voltages plus ground to be used. Ideal for 3.3V devices and op-amps. A basic recharge circuit allows NiMh or NiCd batteries to be charged from a 9V DC source without being removed from the robot.

All spare room on the main PCB is configured as prototype board as show in the picture below. This allows additional sensors and circuitry such as voltage regulators to be easily added.


Of course being designed with parts from LMR it is only fitting that we have the LMR logo on the box.

 Click on the photo for a bigger picture.





More information can be found here: http://letsmakerobots.com/node/24348



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Maybe that'd work for the Mr. General challenge? Hmmm...

I've just seen the Mr. General Challenge (node/12634) and came here for exactly what comes in the kit. I can see a chip is not included but what exactly are you getting? This is what you are getting if I've got it right: (I like lists or my brain melts)

  • IR compound eye
  • 2x38mm diameter wheels
  • Omni wheel steel ball
  • 140 piece cable pack
  • LMR designed sensor bracket
  • 2 factory modified continuous rotation servos
  • 2 mini servos (8g from DAGU list?)
  • A 2xAA battery holder
  • Breadboard
  • PCB

Am I missing anything or assuming anything wrongly? For instance is there a servo motor extension cable with the kit?  Is that a second battery holder as a second power source underneath?

I'm new to all of this so its hard to make complete sense of it all. What I do see is a nice selection of parts and a nice base to work with so I'm certainly interested.

There are 2x 2xAA battery holders to give 4.8V when using NiMh or NiCd rechargeable batteries. There is also another 4x sets of IR LEDs and Phototransistors used on the corners of the PCB to detect edges or objects depending on how you mount them. There is also a small 32ohm speaker and 10uF capacitor which can be connected to a digital output for sound. There is also the usual nuts, bolts, spacers and screws needed to assemble the kit.

No there is no servo extension lead, that is an old photo of a early prototype. I will update this post.

Cheers for the clarification

But I don't quite see why the transistor is necessary?! Can't I just use a digital out pin to feed the Sharp sensor instead of feeding it 5V permanently like I'm doing now? That way I can turn it on/off by setting the digital out signal high/low as required?


Did a bit of research and found that the Arduino digital pins supply up 40mA and the GP2D12 only draws around 35mA. I thought the reason I need a transistor was that the digital pin couldn't supply enough current, but apparently that's not the case. So now I REALLY don't understand the transistor? :/

Yes in theory you can drive up to 40mA from an arduino pin, Be careful not to exceed the current limit for each port and the chip in total. I don't recommend this as the Sharp sensor may pulse the current higher and even if it doesn't you are pushing the limits of the Arduino.

Read the GP2D12 datasheet carefully. The average current consumption is 33mA, Maximum is 50mA

Worse case senario is that you fry you processor or underpower your sharp which may affect it's range. The transistor switch is just a cheap simple garantee that all will work well.

Don't forget that the sharp datasheet notes recommend a capacitor (10uF or more) across the sharps power pins to help absorb the spikes when it pulses it's IR LED.

Thanks :)
If I place the compound eye next to a Sharp sensor (GP2D12) will the two interfere with each other?
You need to disable one when using the other. This is easily done as Mr. Generals IR LEDs are all controlled my the processor and the sharp sensor can be turn on/off using a simple NPN transistor and resistor switch same as shown in Mr. Generals schematics to control the LEDs.
Most likely if they're on at the same time there will be a lot of interference.
Fortunately the 'eyes' on Mr. General can be controlled via the micro, so if you make sure your GP2D12 is also controlled by the micro you can have them activated alternately, so you get almost continuous feedback from both sets of sensors, even though they're never actually on at the same time.