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1246  Using Arduino / Microcontrollers / Re: ATtiny85/84/2313 Reset pin clarification on: February 21, 2013, 12:31:24 am

The reset line has an internal pull-up resistor, but if the environment is noisy it can be insufficient and reset can therefore occur sporadically. Refer to datasheet for value of pull-up resistor on specific devices. Connecting the RESET so that it is possible to enter both high-voltage programming and ordinary low level reset can be achieved by applying a pull-up resistor to the RESET line. This pull-up resistor makes sure that reset does not go low unintended. The pull-up resistor can in theory be of any size, but if the Atmel AVR should be programmed from e.g. STK500/AVRISP the pull-up should not be so strong that the programmer cannot activate RESET by draw the RESET line low. The recommended pull-up resistor is 4.7k Ω or larger when using STK500 for programming. For debugWIRE to function properly, the pull-up must not be smaller than 10k Ω

Personally I've never used a pull up on my programmer boards used with ArduinoISP. If your USB ports are that noisy you've got worse problems than reset pullups.
1247  Using Arduino / Project Guidance / Re: Building gigantic Thermometer need guidance on: February 20, 2013, 09:48:06 pm
How do you define "gigantic"? What dimensions are you considering?
1248  Using Arduino / Sensors / Re: Weight Sensor for small objects on: February 20, 2013, 08:16:32 pm
If the load cell must be read by the Arduino then see for an example. It's not too hard to get right; the most problematic part is getting the gain set correctly. You'll want to use some sort of low value trimmer to get it right. Also, you'll be limited by the precision of the Arduino's A/D converter (10 bits) unless you use an external, higher precision A/D converter.

You still need the load cell of course, and extracting it from a scale like John linked is still a good idea.
1249  Using Arduino / Sensors / Re: Need ideas on tachometer using ignition on: February 20, 2013, 08:10:50 pm
Darlington's are for high-gain. Why use one to take 12V down to 5V?

You still have the noise issue. Any transistor will just amplify the noise as well.

I think Grumpy Mike's idea sounds like the best.
1250  Using Arduino / Microcontrollers / Re: Proper Handling of Reset Pin (When you have no intention of resetting) on: February 20, 2013, 06:29:26 pm
I wonder if the example you're referring to there has a cap connected not to GND for decoupling, but to the RTS pin on an FTDI connection for programming?

Just a few random examples:

1251  Using Arduino / Microcontrollers / Proper Handling of Reset Pin (When you have no intention of resetting) on: February 20, 2013, 12:36:28 pm
Looking at other examples of how the reset pin is handled on AVRs I see the following methods:

1) Leave it unconnected
2) Connect to 5V with a 10K resistor
3) Connect to 5V with a 10K resistor and decouple with .1uF cap

In the particular project I'm working on I have no intention of resetting my chip while it's in circuit; I keep it in a socket and remove it to program. This is also the first time I've built a circuit destined to be used in a small vehicle and I'm trying to make sure I won't get messed up by engine noise.

The datasheet for the ATTiny85 states that the reset pin has an internal pullup when not configured as an input. In that respect it seems like option 1 would be the way to go (noise can't interfere with it?) but I'm open to suggestions on what would be the best practice.
1252  Using Arduino / Motors, Mechanics, and Power / Re: Help me pick a motor driver on: February 20, 2013, 11:56:30 am
1253  Community / Exhibition / Gallery / Re: Arduino Webserver with Temperature Monitor / Control on: February 19, 2013, 11:37:55 pm
There's an Arduino library for "one wire" devices like the DS18B20.
1254  Using Arduino / Project Guidance / Re: Microphone Circuit on: February 19, 2013, 11:24:27 pm
Hi I made a microphone circuit and I plan to make it detect only the wind blowing for my Saxophone project. So far I am having problems on how to do this because when I blow wind to the microphone it gathers data and when I also talk it also gathers data. How can I let my circuit only gather data wind blowing from the microphone?

You could add a second microphone with a windscreen. Subtract signal that the windscreen'd microphone receives. Just an idea.

Here's an example of a blow pressure sensor:

Another thing to add would be a force sensitive resistor where the reed would be. Allow the user to apply pressure with their bottom lip to "bend the tone higher" (damn I played sax for 10 years and don't know the proper term).
1255  Using Arduino / LEDs and Multiplexing / Re: 38khz??????????? on: February 19, 2013, 10:05:58 am
1256  Community / Bar Sport / Re: Cross-posting on: February 19, 2013, 01:01:29 am
Close but no cigar. Or was it something else he was holding onto  smiley-eek
Wasn't holding anything. Was just signing his chances of surviving the full length of the movie (

With respect to the forum tips, I'd suggest encouraging that users set their location in their profile. A lot of answers depend on it (mains voltages, suppliers, etc.).
1257  Community / Bar Sport / Re: Need help fixing my lenovo t61 MBR on: February 19, 2013, 12:56:50 am
You're using recovery CDs/DVDs, correct? They won't care about the MBR; they'll write it themselves. If these rescue CDs are worth a hoot then they should be capable of creating the partitions themselves (replacing the hard drive should be an anticipated scenario) and perhaps undoing any partitioning would be worth a try.

The MBR tells the BIOS were to go on the hard drive to boot the operating system installed there. If there's no OS installed then it doesn't make sense that you could create a MBR.
1258  Using Arduino / General Electronics / Re: Undisputed power to the Arduino on: February 19, 2013, 12:31:28 am
You should look at Tim Nolan's MPPT charger at Not necessarily because you want to do MPPT but because it contains all the elements for controlling power from a solar panel and explains them pretty well. 

NiCD batteries should be charged to 1.45V per cell in the pack; 1.2V is only the nominal voltage. Typical charge rate is 1/10th the amp hour rating. For example, if the battery is 600mah then charge it at a rate of ~60ma.
1259  Using Arduino / Project Guidance / Re: BeBox style Blinkenlights on: February 19, 2013, 12:01:51 am
your bits are backwards. 00000001 is 1, 00000010 is 2....

If you're bad at bit math you might want to use the ShiftPWM library (
1260  Using Arduino / Project Guidance / Re: BeBox style Blinkenlights on: February 18, 2013, 09:49:37 pm
Pretty straightforward to do. See: for examples of how to talk serial to the Arduino.

See for how to control a row of LEDs from the Arduino.

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