Let's Make Robots!

Working on a PICAXE board for robot building - working on v0.9

I'm getting on with making a small PICAXE-driven board similar to the uBotino. I've got it moving along and am ready for other thoughts at this point.

A quick copy/paste from my blog with a little more info:

The Rev-Ed board is nice but there are a few features I don't care for. My PICAXE 20X2 Robot Builder Board does away with/adds those things. And it's only 50mm square.

2nd ed.-

  

post Ro-bot-X mods:

Post CtC and ignoblegnome suggestions (click for full size):

   

v0.6.2 (added switched power to SN754410 per ignoblegnome's observation):

 

version 0.8:

 

The list of features I'm aiming for:

  • Powerful X2 series processor (Rev-Ed's board uses M2/X/M processors)
  • Can use 3AA alkaline, 4AA NiMH, or higher voltage battery packs with the 5V 3A LDO on-board voltage regulator (can be disabled for AA battery packs)
  • Included quad H-bridge driver for bi-directional control of two small motors with power supply selection
  • Option for PWM of motor driver's ENABLE lines for speed control
  • Five pins available for working with servos or LEDs (resistors selected with individual DIP switches)
  • Selectable power source for Port B power header via jumper (allows use of 6V or 7.2V for servos, in particular)
  • Ability to use both SEROUT and A.0 pin on leg 19, jumper selectable
  • Robust screw-down terminal blocks for power connection
  • Power indicator LED

There isn't much wiggle room for adding features but I am eager to hear public opinions, wish lists, wut-i-wudda-duns, etc.

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90 degree corners make noise --or so I'm told. Gotta nip your corners off (of your traces) and make them all 45's around the corners.

 

Hi Jax, I have a few observations about your design. At this moment there are no traces, but I'm sure you'll run into problems if you keep this layout, especially trying to route the traces for the motor connectors (I believe they are Lt and Rt?) I suggest to move these connectors to the side of the H-bridge. Also, it might be better to move the motor power selector to the bottom of the board, so you have more room to route the traces for the second motor connector, first one being directly in front of the motor output pins on the left side of the board (a bit closer to the mounting hole, to make room for the other connector). Moving the motor connectors to the side of the board will allow you to move the 3 pin connectors between the H-bridge and the micro closer to the bottom of the board, making room for the power LED and resistor near the capacitors. Make sure you add 0.1uF filtering caps near each block of 3 pin connectors and near the H-bridge. In theory, all ICs and group of connectors should have a pair of 10uF and 0.1uF close by. Other than that, I can't offer help, as I don't know how Picaxe works.

Good luck with your project!

Gabriel.

Added traces to the post and now I'm studying your words of advice...

Yeah, I was typing while you updated...

One more thing, it is a good practice to have the signal pins in the 3pin connectors allways close to the microcontroller, instead of the GND pin. Most boards respect this pattern, I think it will be a mistake to change it. Oh, and routing the motor connector trace between the microcontroller pins is NOT a good idea. Think of how much electrical noise can screw up your readings or even the microcontroller functionality. Move them away from anything delicate!

It is what it is.

Thought that just linking to the stuff I already posted there would be easiest. Turns out it made for the most work. Odd how that happens a lot...

PCB layout posted here for your viewing pleasure. Just FYI I moved the drill holes in a bit and have not added all the bypass caps in the pic yet.

I keep getting a time out trying to acces the blog you linked.

NIce idea.Have you got any diagrams or pictures to add? I'd love to see it.

Did you try more than one browser? Chrome on my box did open it, after a time.