Sunday, October 2, 2011
Sunday, July 24, 2011
Calculator software
I've done a bit of (very simple) computer programming in the past - mostly scripts to automate some server actions & reports - but never anything with a GUI. Recently, however, a change in some procedures at work has prompted the need for some custom software to bridge sales tracking and cash handling (yawn...). So what the heck does that have to do with Halloween?!? Not much, really, except that in the process of wrapping my head around Tkinter I've managed to write a little utility that encompasses most of the calculations I've written about in the past.
(I know - most of these calculators are available online already - it's really more of an exercise for me. Somebody may find it useful, though.)
There are both Windows and OSX (Intel only) versions. Feel free to download and/or redistribute all you like. All I ask is if you do redistribute it, please link back to this blog. I'd also appreciate any feedback you might have.
Enjoy!
(I know - most of these calculators are available online already - it's really more of an exercise for me. Somebody may find it useful, though.)
There are both Windows and OSX (Intel only) versions. Feel free to download and/or redistribute all you like. All I ask is if you do redistribute it, please link back to this blog. I'd also appreciate any feedback you might have.
Enjoy!
Sunday, June 19, 2011
More on powering LEDs
I've had several questions lately about powering LED spotlights, so I thought I'd see if I can't break it down a little better.
First off, there are 2 ways wire a group of LEDs - series and parallel.
Series: (or what you don't want to do)
In a series circuit, the negative lead of the first LED is connected to the positive lead of the next LED. and so on down the line. In this configuration only 1 resistor is used for the entire circuit. In a series configuration, the number of LEDs you can use is limited by the voltage of your power source. If you have 3 LEDs with 3.6 volt forward voltage wired in series, you couldn't use a 9 volt battery to run them because the total forward voltage is greater than the supply voltage (3.6 + 3.6 + 3.6 = 10.8 volts). I don't recommend this configuration for a few reasons, but mainly because if one point in the circuit fails you'd lose all your lights.
Parallel: (the easy way)
In a parallel circuit each LED has it's own resistor, and the positive leads of all the LEDs + resistors are tied together, and the negative leads are all tied together. When your LEDs are wired this way, the factor that limits the number of LEDs you can use is current (amps).
When you calculate the value for the resistor you need for your LED, one of the values you need for the calculation is the current rating of the LED. If we assume that the calculations are correct, then that current rating is the maximum current that will be flowing through the light. So all we need to do is make sure the total current of all your lights isn't more than your power supply is capable of providing.
So for example, lets say your LED has a current draw of 20 mA. 20 mA (mlliamp) is 20/1000th of an amp, so if you had a 1 watt wall wart, you could run 50 LEDs. I don't recommend loading a power supply to it's full capacity, so I wouldn't run more than about 40 LEDs (80% capacity).
It is possible to wire LEDs in a combination of series and parallel, but I'll go into that another time.
First off, there are 2 ways wire a group of LEDs - series and parallel.
Series: (or what you don't want to do)
In a series circuit, the negative lead of the first LED is connected to the positive lead of the next LED. and so on down the line. In this configuration only 1 resistor is used for the entire circuit. In a series configuration, the number of LEDs you can use is limited by the voltage of your power source. If you have 3 LEDs with 3.6 volt forward voltage wired in series, you couldn't use a 9 volt battery to run them because the total forward voltage is greater than the supply voltage (3.6 + 3.6 + 3.6 = 10.8 volts). I don't recommend this configuration for a few reasons, but mainly because if one point in the circuit fails you'd lose all your lights.
Parallel: (the easy way)
In a parallel circuit each LED has it's own resistor, and the positive leads of all the LEDs + resistors are tied together, and the negative leads are all tied together. When your LEDs are wired this way, the factor that limits the number of LEDs you can use is current (amps).
When you calculate the value for the resistor you need for your LED, one of the values you need for the calculation is the current rating of the LED. If we assume that the calculations are correct, then that current rating is the maximum current that will be flowing through the light. So all we need to do is make sure the total current of all your lights isn't more than your power supply is capable of providing.
So for example, lets say your LED has a current draw of 20 mA. 20 mA (mlliamp) is 20/1000th of an amp, so if you had a 1 watt wall wart, you could run 50 LEDs. I don't recommend loading a power supply to it's full capacity, so I wouldn't run more than about 40 LEDs (80% capacity).
It is possible to wire LEDs in a combination of series and parallel, but I'll go into that another time.
Saturday, June 18, 2011
Friday, February 11, 2011
Sunday, October 10, 2010
Just a quickie
Threw together a couple of lanterns for my yard today.
Pretty simple, really. Just a couple of old jars I dug out of my neighbors garage (with her permission, of course.) I left the inside as dirty as I found them, but wiped the outside so I could dust them with pumpkin orange paint. I wrapped some fine steel wire around the top & twisted it so I could loop handles made from a wire clothes hangers through. I extended the hanger wire over the top & fastened one of the little clip on LED lights from Jacks tool shed. I didn't use the clip - I just taped the light to the wire.
Not sure yet how I'll display them. Thinking about a couple of pumpkin sentinels. Not much time to play...
Pretty simple, really. Just a couple of old jars I dug out of my neighbors garage (with her permission, of course.) I left the inside as dirty as I found them, but wiped the outside so I could dust them with pumpkin orange paint. I wrapped some fine steel wire around the top & twisted it so I could loop handles made from a wire clothes hangers through. I extended the hanger wire over the top & fastened one of the little clip on LED lights from Jacks tool shed. I didn't use the clip - I just taped the light to the wire.
Not sure yet how I'll display them. Thinking about a couple of pumpkin sentinels. Not much time to play...
Sunday, August 15, 2010
Sounds like...
I was looking around for a .mp3 player solution for a prop I had an idea for (more on that later), and came across a couple of boards at MDFly.com.
.jpeg)
The SD/Thumb drive board behaves just like a regular .mp3 player, but has the advantage of having the controls readily available so you don't have to tear one apart & hack the controls to use it. MP3 files can be stored on either a SD card or a USB thumb drive.
The board that really piqued my interest, however, was the serial TTL interface SD board (sold out as of this writing - sorry). This board is controlled by TTL level serial commands, making it a prime candidate for control by an EFX-Tek controller or a pic or Picaxe microcontroller. The board supports direct play of up to 199 .mp3 files, as well as random playback of a single track.
I have both these boards and can verify that they do work as advertised. Now to use them in a prop... :)
.jpeg)
The SD/Thumb drive board behaves just like a regular .mp3 player, but has the advantage of having the controls readily available so you don't have to tear one apart & hack the controls to use it. MP3 files can be stored on either a SD card or a USB thumb drive.
The board that really piqued my interest, however, was the serial TTL interface SD board (sold out as of this writing - sorry). This board is controlled by TTL level serial commands, making it a prime candidate for control by an EFX-Tek controller or a pic or Picaxe microcontroller. The board supports direct play of up to 199 .mp3 files, as well as random playback of a single track.
I have both these boards and can verify that they do work as advertised. Now to use them in a prop... :)
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