Arduino fan’s pay attention, the Mega brother is coming soon. No price or official release date available yet, since the picture is out already you won’t have to wait long to get your hands on this powerful development board.
It’s build around the atmega1280 micro controller, no more excuses that the code won’t fit or isn’t enough RAM, with its 14 PWM channels no motion control application is to complicated and via the 4 USART channels any inter communicating system can be solved.
I can already imagine projects with this board and the ethernet shield: web server, home automation server, security system.
Classic case: all the interesting projects revolve around micro controllers, so you start to dig around and found a dozen of tutorials, how-to’s schematics compilers and so on, you manage to make a simple programmer circuit which is guarantied by some expert from some forum, go out and buy two pieces of atmega8. You have the .hex file, connect the programmer and in that moment your head is full with the data sheet and different settings, you probably remember something about wrong fuse settings could damage the micro controller, and those bits are actually cleared when written, but since you are in a frenzy you click on some fuse settings and load… and then it happens, error reading from device, what could it be, maybe the other IC will work, same fuse settings and load… again the same error.
No more read or write operation, just like the micro controller wouldn’t be attached to the programmer. Most of the thinkers start to measure the supply voltage check the connections and realize at the end that they loaded the wrong fuse settings, and the IC is doomed.
Don’t throw them away in a hurry, you can reset the fuse settings using this parallel high voltage programmer. If you already have the Arduino board this low cost shield can come handy.
For quite a time I was interested about the Peltier coolers, and I ended up buying a small 100W cooling capacity Peltier element. Since you all know, time is always an issue, so this component sit for a year in his box, finally I had the time to try it out.
It’s good to know that standalone Peltier modules do not act as coolers, they just transfer heat from one side to another, from the cool side to the hot side. The simplest way of describing: current is pumped into the Peltier module which translates to pumping heat. Since every current carrying component will generate heat and the Peltier isn’t exception either, beside pumping the heat it will also heat itself.
To achieve the cooling effect it is necessary to dissipate the heat from the hot side, if not the module can reach temperatures above 150-200C and get destroyed. The heat dissipation is made with conventional coolers or forced air coolers.
Now lets talk about numbers, the module I used has 100W cooling capacity when powered from 15V and draws 10A, yes it generates
150W heat to transfer 100W, isn’t very efficient at all since at the end you need to dissipate 250W, which is a lot. Most manufacturers specify also the maximum achievable temperature difference between the cold and hot side, this is usually about 65-79C. So even if you manage to maintain the hot side at 35C, the cool side won’t get below -40C, the good news is that you can stack them up and get larger temperature difference, if you can handle the extra amount of heat generated.
I used a cheap CPU cooler, a small power bench supply for the CPU cooler fan, and a PC ATX supply to power the Peliter.
After applying to the Peltier some thermally conductive grease I mounted a copper plate to the cooling end.
Then I powered the cpu cooler fan, and started the ATX power, you can also check on of the previous post about how to turn the ATX supply into bench supply.
And the fun began, since my PC supply is quite weak the voltage dropped to 10V and with 5A the Peltier was working at its 1/3 of capacity, yet it was able to freeze the water drops on the copper plate in a few seconds:
Important to remember when playing with Peltiers:
1. Always check first which is the cool side or hot side by powering for a short time.
2. Don’t use them without cooler attached.
3. Don’t use thermal grease in excess, it will turn into heat insulator.
4. Always check first the thermal connections.
5. Keep the voltage below the specified maximum. 6. Use sealed type Peltiers, to prevent condensation water short circuits.
You probably wonder if they could be used for heating also, the answer is yes, by reversing the polarity the hot side becomes the cool side and vice-versa, remember always keep the hot side below 150C! And what if you cool one side while heating the other without pumping current into it? You are correct, it will generate current, so the effect is reversible, but the generated current is very small, actually this is the Seabeck effect which is used in thermocouples for temperature measurement.
In overall these Peltiers aren’t effective at all, and draw a great amount of current, but the lack of any moving part makes them ideal when small parts or enclosures need to be cooled.
This is a very simple to build and very powerful power supply for basic electronics, but for a newbie can seem confusing if he tries to make the conversion on its own. The power supplies used in PC’s have useful output voltages like 5V, 12V, 3.3V and even some negative outputs -5,-12V. While the positive outputs can handle significant current, the negative rails tolerate just a few hundred milliamps.
I recently needed about 12 and 10A, since my bench supply can handle only 2A I used an old 250W PC source, on the label was 12V/15A but the voltage dropped to 10V at 5A load, so don’t be surprised if you encounter similar “effects”.
Don’t forget the dummy load on the 5V rail, to be honest I never used it and the supply worked just fine, but to avoid any problems load the output with 0.5A. In lack of power resistor use any 12V light bulb, it will do just fine.
The term POV is for Persistance of Vision, I don’t want to bore you with definitions or explications, just look at the next picture:
The project is very simple, first of all because this type of display is the easiest to build, and because the author made it only for three letters, this way everybody can understand the basic principles and extend the functionalities.
The source code should be optimized and added some position sensing to synchronize the image. The schematic isn’t available but form the source code is easy to reverse engineer, since each led is driven from one micro controller pin.
If you add an accelerometer then you can stabilize the image even when rotating by hand, off course the overall weight must be reduced. With some wireless link you could even refresh the image dynamically.
