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46  Forum 2005-2010 (read only) / Interfacing / Re: watertap connected to arduino on: November 05, 2008, 06:37:55 am
Or maybe a slider pot - but that would probably need to be mounted outside the tap.

Or an LED/LDR combination - as the tap spindle moves down it come between the LED and the LDR progressively causing less/more light to fall on the LDR. Set the LDR up in a voltage divider and measure the change in voltage with the ADC.

47  Forum 2005-2010 (read only) / Interfacing / Re: Powering Arduino in a car on: November 04, 2008, 07:07:57 am
This has been discussed before and from memory the conclusion was that you can power a decimila direct from a car's supply.

(Note, the car's supply is nominally 12V, but when running the voltage is elevated to 13.5 - 14V by the alternator).

My feeling on this is that I would be more comfortable with a regulator of some sort before the decimila. Orac's suggestion of a 7812 is probably the way I would go, but might consider regulating to a lower voltage so the onboard regulator has less to do.

I would probably also over-heatsink the regulator. Am I paranoid? lol

48  Forum 2005-2010 (read only) / Interfacing / Re: What can I use to 'break a beam' ? on: November 04, 2008, 11:18:26 am
Here is a pair of IR devices that are probably suitable:

Also, this project might give you some ideas:

49  Forum 2005-2010 (read only) / Interfacing / Re: What can I use to 'break a beam' ? on: November 04, 2008, 07:00:29 am
What will be braeking teh beam - I guess I'm really asking how long the bean will be broken for.

My initial thoughts would be pulsed infra red into a shielded IR reciever (probably a short tube for shielding).

Sunlight has lots of IR in it (well lots of lots of frequencies of light), so you need to shield the sensor from direct sunlight and the pulsing will enable you to detect your light in high ambient light conditions.

50  Forum 2005-2010 (read only) / Interfacing / Re: phone and Arduino some progress but need help on: November 04, 2008, 07:27:36 am
Float's Mobile Agent: may help a little.

It is a windows application that controls mobile phones - primarily Sony Ericcson phones.

It is written in Delphi, but uses windows scripting to control the phone. You may get some clues from that about how to control a phone.


51  Forum 2005-2010 (read only) / Interfacing / Re: Arduino + Mini Projector? on: November 04, 2008, 06:53:52 am
I think there was a link on this forum to a VGA graphics card tat you send data to over rs-232 serial. Something the Arduino does well.

That projector is really small - about a third of the size of a coke can!

52  Forum 2005-2010 (read only) / Interfacing / Re: Heating coil control with transistor on: November 04, 2008, 06:43:05 am
Finally why rectify the AC why not use a triac as that does the turning off at zero crossing detection for you.

You beat me to it ... I would use a triac for this.


53  Forum 2005-2010 (read only) / Interfacing / Re: Sharp GP2Y0A021YK infrared sensor = sharp gp2d12? on: October 09, 2008, 04:23:06 am
Without taking a close look at the sensors you mention I would answer your question with a "yes, but".

The sketch simply reads a value from the ADC then applies a formula to that value in order to determine the distance.

There is no reason you can't use that method, BUT, the formula is likely to be different for the two sensors.

You should compare the datasheets for the two sensors to see what differences there are. IIRC they have graphs indicating the relationship between distance and output voltage. It is this relationship that the formula is trying to express.


54  Forum 2005-2010 (read only) / Interfacing / Re: debouncing a regular switch with Frequency timer 2 on: October 01, 2008, 03:33:34 am
You do need to keep track of the previous state, or how do you know if the switch has changed / is bouncing.

Also, I think 1ms is too short for a de-bounce time. I have always worked on 20ms. I wouldn't want to go shorter than 5ms.


55  Forum 2005-2010 (read only) / Interfacing / Re: Ambitious project? Maybe. on: September 18, 2008, 08:53:42 am
OK - I'll accept what you say.

So, will an RC ESC do the job?  If so, then that part of the project is sorted - just control it with a RC servo like PWM.

I like the idea of controlling all the air flow flaps - though that could be quite involved. If it were me, I'd leave it for version 2.



56  Forum 2005-2010 (read only) / Interfacing / Re: Ambitious project? Maybe. on: September 18, 2008, 04:24:04 am
I would again suggest controlling the fan speed with a simple motor controller. There are loads of example circuits on this site. You need three transistors, three diodes, three resistors and three relays to emulate the physical switch. Controlling the motor directly will require less components, save a lot of space and produce less heat.

Can you post a link to a suitable circuit on this site?

Whilst I agree with using a motor controller, I have one reservation - that is the power of the motor. The motor control shields shown on this site will not be able to supply the motor. A bigger beast is required leading to complexity and expense.



57  Forum 2005-2010 (read only) / Interfacing / Re: Ambitious project? Maybe. on: September 17, 2008, 03:33:52 am
Here's the difficult part: turning on the fan. My car has a knob with 4 speed settings.

You could do this with 4 relays wired across the contacts for the switch. Being car electrics, the motor is likely to draw a fair bit of current so fairly chunky relays should be used. You can find out how much current the fan is drawing by measurement, or by asking on a forum related to that model of car (if one exists).

You would drive the relays from the Arduino output pins using transistors like TIP120s.

Nice project - there are some interesting parts to it.


58  Forum 2005-2010 (read only) / Interfacing / Re: Getting rid of noise on analogue input? on: September 25, 2008, 07:39:15 am
That's good news.  Well done.



59  Forum 2005-2010 (read only) / Interfacing / Re: Getting rid of noise on analogue input? on: September 25, 2008, 05:24:14 am
Its funny what you learn when looking into things ... it turns out the AVR chip does have a sepearte ground (AGND) for the ADC. So some work on the ground layouts of the circuit can be done if needed.

I'm still a little confused as to your circuit.  Can you post a sketch showing how you have connected to the VCC, AVCC, AREF, GND and AGND pins?

60  Forum 2005-2010 (read only) / Interfacing / Re: Getting rid of noise on analogue input? on: September 25, 2008, 04:51:59 am
My ARef is derived from my power supply and filtered through the previously mentioned 100uF and 100nF caps. I am running the micro at 3.3 volts which is provided by a small switched mode regulator. This voltage is stable.

Have I understood this correctly:

You have a power supply from which you:

a) derive a 3.3V as an external reference for the ADC;
b) supply a switching regulator to produce 3.3V for Vcc.

What circuit are you using to generate the 3.3V reference?

Can you use the internal reference when running at 3.3V?

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