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Noobs guide to connecting parts to a Netduino


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#1 JonnyBoats

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Posted 20 September 2011 - 05:28 PM

I just ran across this excellent, simple guide to connecting external parts to a microcontroller: http://cq.cx/interface.pl#10

It is not Netduino specific, but would work with any microcontroller.

One caution, in his examples he often shows the voltage level as 5 volts, which would be fine for an Arduino or many other microtrollers. The Netduino is a Netduino is a 3.3 volt device so just replace 5 V with 3.3V in his drawings.

He describe how to:

Light an LED from a Digital Output
Read Switch Contacts with a Digital Input
Read a Digital Signal that Goes from 0 V (LOW) to 10 V (HIGH)
Read (with Opto-Isolation) A Digital Signal
Measure a DC Voltage Between 0 V and 15 V
Measure a DC Voltage Between -15 V and 15 V
Measure a DC Voltage Between 0 V and 1.7 V
Measure the Position of a Potentiometer
Measure an Unknown Resistance
Measure a Temperature
Output Characters on an LCD
Switch a 100 mA, 10 V Load
Switch a 1 A, 10 V Load That Always Stays Connected to Ground
Switch a 10 A, 40 V Load
Switch a 120 VAC Load

#2 Bill E.

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Posted 21 September 2011 - 12:33 AM

JohnnyBoats, What an excellent link! Good find. As an EE I read the first few "how to" articles word-for-word. After that I was skimming through very fast & having my eyes "roll-back" with the tech details. No dis-respect!! No way! I appreciate and admire the content, author, your mention of the link. First off, I just returned (less than 48 hours ago) from a 2 week vacation trip to Japan and am still in a "jet-lag" stupor. Second, I am SOOO glad to be back & getting back to the forum. For the folks that can't follow, or cannot grasp the tech-details of the link, allow me to add my 100 yen (that's about $1.40 now!). 1. Our microprocessors/microcontrollers have a huge number of I/O pins which is so fantastic!! But watch for the total, combined I/O current consumed (which means POWER produced). That is, if every pin can sink/source, let's say, 25ma, and you are driving 100 LEDs, you can potentially be asking the IC (microcontroller) to deliver 2.5 Amps and, sad to say, ain't going to happen. Ohm's law works for voltage, current, resistance, power, uhhhhmmm, did I miss anything??. Look at the spec sheet for the particular micro for "total current used" or similar. This doesn't mean diddly for inputting to the micro. 2. Really be aware of the input "VOLTAGE". Remember, CURRENT is derived from the resistance between the source and, for lack of a better term, GROUND (or REFERENCE). If you have 100 Volts "across" 10 million ohms there cannot be more than 10 micro amps of current flowing through that resistance. BUT there is still 100 Volts "potential" aross that resistor. Internally to the micro IC, it will violate in a BIG way its circuitry and end up in major smoke. Look at the Parallax BS2 "Serial" input specs. The pins can tolerate a negative 12V to positive 12V signal and still survive because the current and voltage specs are within the PICs "input" specs. Jet lag babbling now! Post your questions/comments & let's see if we can design the next generation space shuttle!




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