Building Hexapod robot, please recccomend parts for cheap build

[davidom2513]

I am planning to build a hexapod robot for a college project, with 18 servos, probably towerpro MG995 or SG5010. I will build the body and legs myself out of plywood. Can people please recommend what other parts I need for the cheapest build possible.

If I get this mini maestro 24 channel servo controller from pololu, do I still need a microcontroller and other parts? If so how would I connect it to the servo controller?
http://www.pololu.com/catalog/product/1356
                                                                         
I would also like to be able to control the hexapod wirelessy, either by a control pad or an android phone. What is the best way to acheive this?
If that becomes too expenssive I could control it from the pc.

I am open to suggetions from people, so please give me your advice and reccomendations.

Thanks in advance,
David

[rbtying]

You could try to make a hexapod without another microcontroller, but it will be incapable of doing anything other than walking (no space for sensor inputs and such).  Realistically, with 18 servos, you're already well over the point where a $5.00 microcontroller is a good investment =). 

Wireless communications are expensive - if you want Android comm, you'll need to use bluetooth, which generally runs at ~$40-$60 per robot.  PC control, if wired, is cheap - but if you want that wireless, you're back to the same expensive comm problems. 

Also, plywood's a little heavy for a hexapod - consider using acrylic or another light thermoplastic.  Servos are already quite heavy - increasing the load doesn't work out well, usually.

[davidom2513]

Thanks for the response rbtying,

It would be great if I could get a microcontroller for it for around $5. Do you know any suitable ones for that price? would it need to have 18 o/p's for the servos then? And also I am very confused about how I would go about connecting the microcontroller to the servo controller, where would I connect the microcontroller?

My preffered method of control would be with my android phone, so if I cannot find a cheap bluetooth module, I will control it with wires from the pc. would this be suitable, it is also cheap.
http://www.sparkfun.com/products/8497

yeah, your probably right about the plywood, thanks for the suggestion, I'll look into the acrylic

[rbtying]

That bluetooth module is fine if you're willing to work with a surface-mount device (read the datasheet to figure out which pins are important). 

As for a microcontroller, the ATMega328P is nice and well-supported around here, although programming it will require an external programmer.  You could also get the one with an Arduino bootloader preloaded and use a usb-serial cable to do the programming.  If you want a fully developed board, you could get the Arduino Pro Mini, which includes the external components you will need to make the board run. 

You will want to have a servo controller and another microcontroller - 18 servos is pretty significant, and splitting the load is generally going to make your life much easier.  If you want a self-contained unit, you'll have to use a more expensive microcontroller: perhaps the Axon, or a Spider Controller. 

[davidom2513]

Yeah I'm willing to work with smd as long as it doesnt prove too difficult to use it and connect it.

How would I go about connecting up the chip with the bootloader using the usb-serial, I'd probably still need an adruino

I checked out the Arduino Pro Mini there, and i'd need to buy a ftdi cable to program it, as it doesn't have the connections on board. That would cost another $18. So, maybe the Arduino Uno with the ATMega328P would be the better option, as it costs $30 and can be programmed without addidtional wires. What do you think?

Or I could go with this basic micro ARC32 instead, its an all in one servo controller and microcontroller. and I could control it with a ps2 controller as it has a port for it, they would both work out around the same price.
http://www.basicmicro.com/ARC32_p_141.html

The 24 servo controller, adruino uno, and smd bluetooth module together cost $123 delivered
while the ARC32 would cost $118 delivered and I can get a ps2 controller for $12
The servos will cost $116 delivered. In total thats around $240

Its getting a little bit expensive, unless I just control and power it from a computer. Let me know what you think.
Thanks

[garrettg84]

Check out the paralax propeller chip. It is orders of magnitude faster than most of the AVR chips. With a propeller or two you can actually bit-bang usb host and use one of the cheap 2 dollar bluetooth adapters from amazon.