PID Hardware Photos

I was (and hope to again) working on a PID loop for the dragon’s main light. The idea is simple- vary the heat lamp using a servo and rheostat. Some of you have expressed interest. Here are the photos of the servo setup. The code however is so bad I don’t even know where to start. If you get something working please let me know!

The servo and linkages work perfectly through the full 180 degree range. The issue is the PID code….

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PID? What is it?

Wikipedia says that a proportional–integral–derivative controller (PID controller) is a generic control loop feedback mechanism (controller) widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an “error” value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process control inputs.

So what?

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Out of I/O! What to do???

My LCC project is growing. Too much I/O is needed! I’m exploring the I²C bus system. It seems simple enough.

Direct I/O is nice but is wasteful- I’ve used all the I/O already on the LCC project but I still need more! Wikipedia has a great write up all about it. Now I have to apply it to Arduino!

Using a Transistor to Control an LED or anything

For my LCC project I decided to use a 2N4401 NPN transistor to control status LEDs and AC Switches. I did this so that the power draw from the Arduino chip would be as low as possible.

Below is a diagram of how this works. I used a 2N4401 NPN transistor that “turns on” when the gate goes high or positive. This essentially allows it to switch the negative or ground leg of the circuit. I did this because the Arduino can’t turn a digital IO line to ground- just 0v or 5v. Continue reading “Using a Transistor to Control an LED or anything”

Slow Button/Switch Reaction

On my last project– which still isn’t done yet- the buttons for changing the temp display are very unresponsive.

The reason of course is because the Arduino has to loop through all the main code before getting around to checking the button status.

I found the cure! Interrupts!

EngBlaze has a great write up on how to use this. Whew! One less I have to write! Read it here. I’ll be modifying the Tri-Temp code to use interrupts soon. Sweet!

Tri-Temp Project Intro


This is the Tri-Temp project. It comes in two flavors- Standard and Ethernet. The Standard version outputs all readings on an LCD. The Ethernet adds output to HTML via a web browser. I did not design this to use an Ethernet shield- only the Arduino Ethernet- it’s more compact.So what’s this all about? Reading the Temp and Humidity! Nothing special going on here, just reading the digital data from three DHT22 sensors and displaying it.

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DHT11 Digital Temperature & Humidity Sensor

This was my first sensor. It’s a digital temperature and humidity sensor. It uses three pins, two for power and one for data. It worked perfectly…except….the libraries provided by Virtuabotix ($9.99 via didn’t work with the Arduino IDE v1.0.

So if fixed it!

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