Show Posts
Pages: 1 2 [3] 4 5 ... 14
31  Forum 2005-2010 (read only) / Interfacing / Re: using a touch screen from a phone on: March 21, 2008, 12:48:56 pm
Quote
I can understand that i put 5v Across one of the pairs (1 and 3 or 2 and 4)of they act like the two outside pins on a pot and when i pres the screen one of the wires in the other layer becomes the wiper and i can read one of the coordinates from that.

But how do i read the other coordinate without changing the way it is hooked up to the Arduino pins ?

You energize one pair using output pins from the arduino, not a 5V supply. Then you set those two port pins to inputs and power the other pair from other output pins.

Does that make sense?

Mike
32  Forum 2005-2010 (read only) / Interfacing / Re: using a touch screen from a phone on: March 19, 2008, 07:37:29 am
Quote
got it working! after some very fiddly soldering! cheers gang, i just plugged it straight into the arduino, works pretty well.

That's good news, Jim. I was so tempted to get one of those screens, but I have enough projects in line for these Arduinos as it is.

Do you have a project in mind for it?

Mike

33  Forum 2005-2010 (read only) / Interfacing / Re: using a touch screen from a phone on: March 19, 2008, 07:30:14 am
Quote
So let me se if i get this right. i apply 5V  and ground to two of the 4 wires and the others are hooked up to analog inputs on the Arduino board an treated just like any other variable resistor ? each giving me a number for the X and Y position on the screen ?
 

You have to apply the 5V across one pair then read the analogue value from one of the wires in the other pair, then apply the 5V to the other pair and read the analogue voltage from one of the wires in the first pair.

It is that easy, though in a commercial environment you would have to calibrate the x and y values so top left and bottom right etc are accurate, also to prevent build up from electrolysis you would reverse the voltage on the pairs, you would debounce the touches, you would have a sleep mode with touch detection, some filtering of the values is desireable and if you are using it as an input device to replace a mouse, you need to be able to detect a "click".

None of this is necessary in simple applications, though.

Regards,

Mike

34  Forum 2005-2010 (read only) / Interfacing / Re: using a touch screen from a phone on: March 12, 2008, 10:15:11 am
I've used Wasp's touch screen in the past - here is a nice page about them:

http://waspswitches.co.uk/english/touchscreens_4wire.shtml
35  Forum 2005-2010 (read only) / Interfacing / Re: using a touch screen from a phone on: March 12, 2008, 10:09:10 am
It looks like it would be an analogue resistive type of touch screen - there appear to be 4 connections and two of them lead to lines that go up each side. I guess the others lead to lines across the top.

They will handle 5V without trouble.

Here is a wikipedia article for a quick intro on how they work:

http://en.wikipedia.org/wiki/Analog_resistive_touchscreen

and this one gives more info:

http://en.wikipedia.org/wiki/Touchscreens#Resistive

It would be worth reading through the spec sheet of the chip nima mentioned to find out how they do it - then implement it in code in the Arduino (or just use the chip).

They seem to be reasonably priced in that auction. FWIW, I have purchased from that seller recently without problem smiley

Regards,

Mike
36  Forum 2005-2010 (read only) / Interfacing / Re: using a touch screen from a phone on: March 12, 2008, 06:29:08 am
jimmeh,

nima's link is a good one - however, you may be able to drive the touch screen from the Arduino itself.

It'll take 4 pins - 2 digital outs and 2 analog ins.

Simply, you apply 0V and 5V to one axis and read a touch value from the other. Then do the other axis.

I did this with a PIC a few years back.

Regards,

Mike
37  Forum 2005-2010 (read only) / Interfacing / Re: Question about imprecision of Analog Input on: February 16, 2010, 10:19:04 am
Another thing you could try is connecting a bandgap refence to the pin and see what the range of values is - maybe supply it from a battery.

As you have an analogue background, you'll understand the importance of good earth routes and separating the "power" grounds from the lower signal grounds.

I looked into this a while back and, from memory, the Atmel chip has separate analog and digital supply and ground, but the Arduino guys tied these together on the board. This won't help keep the converter noise down.

If you have an Arduino with a DIL processor, you could pull the analogue section legs out and see if you can make improvements like that.

Other than that you're down to implementing some filters in firmware.

Regards,

Mike

Arduino schematic:
http://www.arduino.cc/en/uploads/Main/Arduino-Diecimila-schematic.pdf

38  Forum 2005-2010 (read only) / Interfacing / Re: LM34/35 temp sensor on: September 18, 2008, 08:38:27 am
Numbski,

the ADC on the AVR chip on the Arduino has a 10 bit resolution.

Regards,

Mike
39  Forum 2005-2010 (read only) / Interfacing / Re: analog out 0-10V With Arduino for lighting con on: July 22, 2008, 03:42:09 am
Quote
And how should i «smooth it into a true analog level first»?.  
Mike sais that i need a low pass filter the circuit to smooth out the PWM pulses to DC.
Any Schematics? ...
 

The schematics for a low pass filter are in the pdf I linked to:

http://instruct1.cit.cornell.edu/courses/bionb440/datasheets/SingleSupply.pdf

Regards,

Mike
40  Forum 2005-2010 (read only) / Interfacing / Re: analog out 0-10V With Arduino for lighting con on: July 18, 2008, 11:33:42 am
You might find this document to be useful ...

http://instruct1.cit.cornell.edu/courses/bionb440/datasheets/SingleSupply.pdf

You will need a low pass filter circuit to smooth out the PWM pulses to DC.

Mike
41  Forum 2005-2010 (read only) / Interfacing / Re: Foot position sensing on: December 02, 2008, 11:38:52 am
Tricky problem.

How fast do you need to measure the feet positions?

I've been musing along the lines of a flatbed scanner.

(I know a scanner isn't suitable, but can one nick an idea from it?)

Mike
42  Forum 2005-2010 (read only) / Interfacing / Re: Interfacing the XPort Direct on: October 06, 2008, 05:17:08 am
Sorry about the clip - I thought you were using one of these:



If your device doesn't get warm, it doesn't need any extra heat sinking.

Well done for getting it going.

Regards,

Mike


43  Forum 2005-2010 (read only) / Interfacing / Re: Interfacing the XPort Direct on: September 30, 2008, 04:09:50 am
The spec for the XPort says that it needs areas of copper on the PCB to help with heat-sinking.  The first release of the ADAFruit shield did not have this.

One of these should help:



Regards,

Mike

44  Forum 2005-2010 (read only) / Interfacing / Re: Interfacing the XPort Direct on: September 29, 2008, 10:36:36 am
For prototyping, you can use a small length of ribbon cable.

Note that the XPort needs some additional heatsinking - a bulldog clip is probably enough smiley

Regards,

Mike
45  Forum 2005-2010 (read only) / Interfacing / Re: ArduinoBT: Why so expensive? Alternatives? on: June 09, 2008, 04:07:39 am
Lantronix do WiFi modules - not cheap, but may offer you something additional to make it worthwhile.

Mike
Pages: 1 2 [3] 4 5 ... 14