How to add Touch Sensors?

[BillB]

I am contemplating adding touch sensors (binary switces)to my Robonova. I have reasoned that few (up to 4) on the bottom of each foot could be useful for maintaining balance (perhaps more useful than Gyros - will see) and a few on other swiches in strategic places (arms, knees etc) for obstacle detection.


But unfortunately I don't know how to interface a large number (initially 16) binary switches to the robonova controller.

Does anyone have suggestions to how this can be done?

[hivemind]

I would think that you would need to have them be on the AtoD ports, and you might want to power them off the battery directly because the MR C-3024 board only has a few hundred mA, and not that much to spare.

Supposing you could even link the system up you would need more control than the robobasic provides. You would most likely want a real time control so you could control the feet touch sensors over variable terrain, yes? But robobasic will not allow this, and furthermore will not allow a variable type move command.

Sorry I have to dash your hopes a little here, and I certainly hope one could find a way around this, but I hoped to help by making you aware that there would be some difficulties you would need to deal with.

Goodluck to you, it sounds like a great project if you can find a way to get it working.

[Robo1]

Hello

One way you could do it would be to have a pic or another proccessor running your switches then have that sending commands to the controller. the problem would be geting the system to work in real time and making the control board do something useful with all this information.

bren

[NovaOne]

But unfortunately I don't know how to interface a large number (initially 16) binary switches to the robonova controller.

Does anyone have suggestions to how this can be done?

I BillB are you still considering this or have you done it?

I've been considering this, wth very small microswitches, 8 per foot using a MCP23016 I2c i/o expander.

But do you think Force Sensing resistors would be better like the ones JonHylands is selling for the Bioloid?

Chris

[BillB]

To tell you the truth I have focussed my efforts on the Bioloid since my last posting on this thread. I am patiently waiting for JonHylands foot sensors - so I can try out concept.

[Humanoido]

If you get back to this project, a small Basic Stamp 2 microcontroller from Parallax Inc. has 16 ports, perfect for sensing 16 switches each on a discrete line. You could also put several switches on the same line with some resistors and read the values through analog to know which one was activated. Also, the BS1 has a button command in PBASIC which could be very useful.

humanoido

[NovaOne]

I considered using a micro controller, but i am using what i believe to be the cheapest option, for a change ie

Basic stamp 2 from milford instruments (http://www.milinst.com/) in the UK is £30

For this simple task I thought simpler controller would do the trick eg a:

PICAXE18 from http://www.techsupplies.co.uk for £2.50

Then I looked at the MCP23016 i2c I/O expander which from http://uk.farnell.com/ they only cost £1.31

Humanoido this question is for you:
I would like to add lots more distributed processing power to my RN, by using extra micro controllers maybe even a gunstix , but assuming i do not have a free UART or many free ports, what is the best way for them to communicate with one another?

Chris

[i-Bot]

I just tried my new I2c Master patch which I added to the C3024. This adds a new I2C master controller on the PWM0 and PWM1 pins

After a couple of design iterations, I ended up using unused BYTEOUT and BYTEIN addresses, and made a generic I2C which should be flexible enough to talk to any I2C device. You can send/receive any I2C sequence, even sending and checking NAK.

I used to SP03 code from NovaOne as a test comparison. The I2c part of that takes about 2 seconds in the original bit bang code. The new I2c master takes 35 millisec.

If this is not fast enough, we could encode the full support for the Microchip I/O expander or the PCF8574, and get it down to a couple of millisec.

I will post more in the "need for sound" thread

[NovaOne]

Thanks i-Bot, you are a true genius

Are you going to ROBOtic'07

Chris