As the HEV Suit model has some lighting in it, I definitely want to have it in my own suit as well. Not only will it look complete, but those lights will most likely make the suit look awesome in low-light conditions. While the only experience I have with soldering is repairing my old stereo which needed some new electrolytic caps, something as basic as LED’s wired in parallel should be more than doable to me. As I’ll be adding lights anyway, I’ve also decided to make the Lambda on the front illuminated for added eye-candy. Finally, considering how warm foam costumes tend to get I’ll also incorporate an intake fan into the costume where the “charging plug” would normally be. Hopefully having some form of airflow will greatly assist me with staying cool as I move around in the costume…
For the LED’s I will be using USB power banks. The ones I own provide 5V with a max draw of 2A, which is more than enough to power the 20~24 LED’s. Each LED will be wired in parallel with a resistor in front of it to prevent the LED from burning out. The value of these resisters can be calculated with a basic formula; R = (Vs – Vled) / Iled. R is the value of the resistor you will need, Vs is the voltage provided by your power supply (in this case a power bank), Vled is the voltage the voltage drop from the LED’s, and finally Iled is how much current in Ampere the LED’s draw. However if this sounds like pure hocus pocus to you there are plenty of online LED resistor calculators available, some of which even give you schematics on to wire them properly.
In the schematic above L1 is a white LED running at 3.3V with a 20mA draw, while L2 is an orange LED running at 2.1V and a 20mA draw. In total 18 white LEDs will be used, and about 6 orange LEDs. Together they add up to a total power consumption of 357mA, which is well within the reach of even a standard USB port which grants you a max draw of 500mA, as well as the 2A max draw provided by my power bank. Using another formula I can calculate how long each power bank can power the LEDs; Estimated Hours = Battery capacity in mAh / device consumption * 0.7. The magic number 0.7 is there to keep external factors like ambient temperatures in mind. In my case I have two power banks, one with a capacity of 6200mAh and one with a capacity of 10,400mAh. In other words, the first will last me ~12 hours while the second power bank will last ~20 hours on a full charge. In other words, more than enough time to last me all day before I get back to my hotel!
The fan I’ll be using will be either a 10 or 12cm computer case fan. The beauty of case fans is that are cheap to come by and often operate between 7V and 12V; the more volts you supply to them, the faster they spin. To power these I have four options;
- Use a USB step up 5V to 9~12V converter with my power bank. These are relatively expensive unless you trust cheap Chinese versions, which I don’t.
- Use 9V block batteries. Normal versions offer around 500mAh, or ~2 hours per battery. This means that for an 18 hour day I will require 8 batteries per day, which adds up to €15 a day.
- Use 9V lithium block batteries. These offer 1200mAh, or ~5.2 hours per battery. While I wouldn’t have to replace them that often I would still need at least 3 of them each day, which adds up to €27 a day.
- Use 6 1.5V AA batteries in series. This solution gives me 2600mAh, or ~11.3 hours per six batteries. This means I’ll have to bring more batteries with me, but given the low cost of AA batteries it seems to be the best solution as a 24 pack only costs €9,99, meaning it will only cost me €4.40 a day. I better not forget to hand in the dead batteries for recycling…
Aside from the power supply the only other component I’ll use is a switch, which is incorporated into the battery pack. Before I do any soldering however I’ll create a bread board version of both circuits just to make sure nothing starts burning up as the last thing I want is to cosplay the Samsung Galaxy Note 7. But, more on that next time!