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1306  Using Arduino / General Electronics / Re: TLC5940 - 1st works, 2nd not :/ on: February 14, 2013, 03:59:28 am
Oh snap.

So you why don't you have the SCLK connected between the chips? Each chip will need that signal.

Not clear on the purpose of the GSCLK but it seems that should be connected as well.
1307  Using Arduino / Motors, Mechanics, and Power / Re: Big easy stepper motor not changing direction. on: February 14, 2013, 03:07:12 am
Im sure its alle wired up corectly but its not changing direction when I run the program-

Does that mean that you're reverse the counting in the program or what?
one direction: 00, 01, 11, 10,...
other direction: 00, 10, 11, 01,...
BigEasyDriver has a step/dir two wire interface.

OP, what program are you using to drive it?
1308  Using Arduino / Sensors / Re: Ds18b20 long wire problem on: February 14, 2013, 02:46:25 am
Maxim provides an appnote discussing this:

If you want better answers you should provide more detail as to your topology and how long your cables are.
1309  Using Arduino / Sensors / Re: Is it possible to use the Sensors for this on: February 14, 2013, 02:41:35 am
Look for IR reflectance sensors used for "line following" robots. sells a few and provides theory/schematics/instructions.
1310  Using Arduino / Sensors / Re: Need ideas on tachometer using ignition on: February 14, 2013, 02:39:23 am
This would be an inductive sensor when you're wrapping a wire around the spark plug wire. The current flowing through the spark plug wire induces a current in your coil.

The Arduino pins are protected by what are called "clamping diodes" that will protect the pins from high voltage currents under 1ma. I wouldn't expect to see more current than that from your inductive sensor unless you use a large number of wraps of wire, but if you want to add additional protection you would add a resistor between the coil and Arduino input as well as a 5.1V zener diode between the input and ground (coil -> resistor -> zener cathode -> analog input). Zeners are like regular diodes conducting from anode to cathode with a .7V drop, but also conduct cathode to anode when the voltage is over their rated breakdown voltage.

How many times you should wrap a wire around the spark plug wire and what size resistor you should use is hard to say. Perhaps the simplest way to test would be to connect both ends of your coil to an LED and judge by the brightness of that LED.

Expect a lot of electrical noise to mess with your readings as well. That is why there aren't any "easy" schematics used in this situation.

1311  Using Arduino / General Electronics / Re: TLC5940 - 1st works, 2nd not :/ on: February 14, 2013, 12:42:13 am
Did you adjust NUM_TLCS in tlc_config.h and delete the existing Tlc_5940.o file so the change will take effect?
1312  Using Arduino / General Electronics / Re: supplier for flatted-shaft knob without pointer on: February 13, 2013, 12:04:46 pm
Also check musical instrument suppliers; electric guitars use the same non-pointed knobs you need and some supplier sites have a dizzying array of pretty fancy knobs.
1313  Using Arduino / Project Guidance / Re: power Arduino - 12V car battery on: February 13, 2013, 12:00:09 pm
Yes, if the battery is not connected to a car. If the battery is connected to a car you should anticipate a lot of noise in the power lines.
1314  Using Arduino / Project Guidance / Re: arduino codes to measure speed of a falling simulated raindrop on: February 13, 2013, 11:54:36 am
Ready for the buzzkill? From the TSOP1738 datasheet:

After each burst which is between 10 cycles and 70
cycles a gap time of at least 14 cycles is neccessary

TSOP1738 doesn't allow you to create a continuous beam; it will reject it after 70 pulses. You need a "fixed gain" (Vishay TSSP4038 et. al.) receiver to create a continuous beam. Might be worth mentioning that those fixed gain receivers are a bit hard to come get your hands on.

Also see how the Camera Axe implements a projectile sensor:

1315  Using Arduino / Project Guidance / Re: 3w RGB color bar (BOM w/ TLC5940, Fets, UNL's on: February 12, 2013, 09:43:11 pm
Would I a pull-up in this scenario, like a 10k pull-up between ADJ and controller's output?   
would it be close to this model below?
(each color 350ma)

3ch RGB controller output1(12v >)  -> 10kpull-up -> Adj 
10kpullup -> c1=100nF -> Grnd

The RGB controller output goes to the gate of an NPN transistor, the collector connects to the open collector output, and the emitter connects to GND.
1316  Using Arduino / General Electronics / Re: What is the minimum wiring for two switches? on: February 12, 2013, 12:48:31 pm
The IO pins are all set to input / high impedence when the chip is first powered on or after a reset. Nothing will be "on" until you explicitly command it in your code.

It's a safety thing, or just makes sense I guess.
1317  Using Arduino / General Electronics / Re: The ants come marching in (and release magic smoke) on: February 12, 2013, 12:37:22 pm
The ant by the SOIC 8 is sitting between the source and drain that handles the switching of the AC in the transformer.
1318  Using Arduino / Project Guidance / Re: ARDUINO as a RPM limiter on: February 12, 2013, 11:59:09 am
I would be interested in this for an automotive application any way to get over the overheating issue?

You reduce the amount of time that current is flowing through the coil (the "dwell" time). It should only be energized for a very short period before you switch off the current / create the spark. Just take a close look at your distributor and you'll see the the breaker points are only closed momentarily.

There are special purpose IGBTs/mosfets designed for this type of high voltage current switching; a dig around Fairchild Semi's site will list a number of them. Or use the google, etc.
1319  Using Arduino / Sensors / Re: Calculating Vehicle Position with an IMU on: February 12, 2013, 01:26:49 am
"Optical Flow Sensor" like a mouse. used to sell a nice breakout with a sensor and a lens but it looks like they discontinued it. I understand the most difficult part (aside from the code) is finding an appropriate lens so you can get the floor in focus for the sensor.
1320  Using Arduino / Sensors / Re: Peizo Sensor to detect hits from a bat on: February 12, 2013, 01:15:25 am
Good link for filtering piezo signals:
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