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24466  Forum 2005-2010 (read only) / Interfacing / Re: volt, temprature, amps and watt meter on: October 21, 2010, 09:38:11 am
Thanks for the clarification we now know what you want. A design complete with schematic and software.
Now it is just a matter of seeing if anyone has come across one for you.
24467  Forum 2005-2010 (read only) / Interfacing / Re: volt, temprature, amps and watt meter on: October 21, 2010, 07:25:17 am
First off you don't measure the watts you calculate it from the measured voltage and current.
Do you know what range of current you want to measure, hall effect current sensors only give you values down to about half an amp.

24V is a bit on the high side for powering an arduino, you have to look at the capacitor voltage ratings.

Finally are you looking to learn how to design such a system or do you just want to build one?
24468  Forum 2005-2010 (read only) / Interfacing / Re: serial communication GPS on: October 21, 2010, 05:49:49 am
Not necessary on this forum threads sort of just fizzle ou.......  
24469  Forum 2005-2010 (read only) / Interfacing / Re: serial communication GPS on: October 20, 2010, 08:18:45 am
Put an LED and 1K resistor across the input and see if it is flashing. This checks if there is a signal coming from your GPS and making it into the arduino.

After that check the baud rates.
24470  Forum 2005-2010 (read only) / Interfacing / Re: Cheap IR or another option? on: October 21, 2010, 03:19:03 am
No those two devices are entirely unstable for what you are doing. You want a simple reflective opto switch something like this:-
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=1714930
It is possible to get them much cheaper that this if you look around, less than $1.00 from some places.
But just get one to try before you go ordering lots.
24471  Forum 2005-2010 (read only) / Interfacing / Re: PWM of 7-segment led with common anode? on: October 21, 2010, 03:11:50 am
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A "high side" current switch should be a PNP transistor
Or it could be a p-channel FET, make sure you get a logic level one like I used here:-
http://www.thebox.myzen.co.uk/Hardware/Mini_Monome.html

I would agree with rugged about driving the cathodes through a ULN2803 or similar sink.
24472  Forum 2005-2010 (read only) / Interfacing / Re: High pitch whine from LCD normal? on: October 21, 2010, 03:08:09 am
Sometimes the back light of an LCD is a cold cathode tube. This requires a high voltage to drive it and it is supplied by an inverter. If so you can generally hear a small noise from the inverter caused in main by the wire in the inductor moving as magnetic fields pulse in it.
24473  Forum 2005-2010 (read only) / Interfacing / Re: Using RX/TX as digital IO... on: October 19, 2010, 03:07:48 am
The main problem is that when you upload stuff external circuitry connected to the line will:-
1) Go up and down.
2) Possibly override the signals from the serial port.
The best bet is if you arrange to switch out the external circuitry whne you upload to the board like in this project:-
http://www.thebox.myzen.co.uk/Hardware/MIDI_Shield.html
24474  Forum 2005-2010 (read only) / Interfacing / Re: MPR121 capacitive touch sensor mystery on: October 20, 2010, 04:01:52 pm
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didn't change the registers, why were the thresholds okay yesterday)?

Because it is not a robust technique and just a demo sort of thing without a PCB as the sensor.

Have you wired the board to 3v3 or 5V?
24475  Forum 2005-2010 (read only) / Interfacing / Re: Reset Serial? on: October 19, 2010, 09:28:48 am
@Bob:- that link is the auto reset on the main serial connection. This seems to be a problem with two of the extra serial ports on a mega, not the main one which is still called serial (not serial1).
24476  Forum 2005-2010 (read only) / Interfacing / Re: TLC5940 Resistor on: October 20, 2010, 03:57:34 pm
No worries we all have to learn it.
24477  Forum 2005-2010 (read only) / Interfacing / Re: TLC5940 Resistor on: October 20, 2010, 01:20:13 pm
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I believe that they are meant to sink voltage.
No they sink current.

Sinking voltage is a phrase that doesn't make sense.
24478  Forum 2005-2010 (read only) / Interfacing / Re: TLC5940 Resistor on: October 20, 2010, 03:56:37 am
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Will I need to make adjustments if I don't use all the driver pins?
No.

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And can I use different voltages on each driver pin?
Well I have never thought about that but providing they are all less than 12V (I think check the data sheet as it could be 17V) then I don't see any reason why not. Make sure all the grounds are together.
24479  Forum 2005-2010 (read only) / Interfacing / Re: TLC5940 Resistor on: October 19, 2010, 02:51:11 am
The whole point of the TLC5940 is that it has a constant current driver. The single resistor sets the current for all the LEDs. Just because you currently don't understand it is no reason to abandon it. I am not even sure if what you are asking is possible, I know it is not desirable. You will in effect be driving the constant current drive outside it's normal operating conditions.

Look at the data sheet and see what vale of resistor you need for the current you want, there is a graph so you don't have to touch any scary maths.
24480  Forum 2005-2010 (read only) / Interfacing / Re: output pin mapping to shift register or similar on: September 30, 2010, 02:53:13 am
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The thing i am looking for is not magical at all... an ordinary shift register or GPIO chip, simply with software that is beyond my current skill to produce

Or indeed given the constraints:-
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I want to make it work with libraries, without modifying said libraries.
beyond anybodies current skills. Or indeed future skills with out the evocation of magic (which you have also ruled out). In short no you can't redirect pins from a library to your own driver without changing the library or rewriting the whole of the foundations of the system.
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