I found a nice breadboard in McGill’s garbage a while ago and decided to convert it into an electronics bench. My main goal was to have a powerful power supply with regulated outputs combined with a breadboard and some useful connectors so I can build circuit prototypes easily. Also, I needed a new bench power supply since mine was lost in the Lunar Excavator shipment.
Materials
A nice breadboard found in the garbage
A computer power supply
An ATX motherboard power connector
Two LEDs with resistors for current limiting
A switch
Some cables
Putting it Together
I wanted to build a modular system so I can replace the pieces easily, especially the power supply (since it comes from an old computer and may not work for very long).
I connected a switch and two LEDs (actually, my switch comes with an integrated light so I used only one LED) to the PS ON, 5V SB, and PWR OK pins so I can have an indicator of the power supply (PS) being plugged-in (D1) and another for the PS being turned ON (D2). The diagram below illustrates the connections.
I also connected the 12, 5, 3.3, 0, -5, and -12 V lines to the bottom-left banana connectors in order to have easy access to the power lines. Now, I can connect any ATX power supply to the box and it will work, which makes replacing a defective power supply very easy.
After making the electrical connections, the switch and LED(s) have to be mounted to the box by drilling appropriate holes.
This was a fairly easy build, with the only difficult part being to find the appropriate materials in the garbage.
I may add a USB hub or some USB connectors as well in order to have more ways of connecting things to the box.
I received many questions about the circuits driving the LEDs in many of my projects, especially for the Iron Man’s repulsor.
LEDs are pretty neat devices. You make some current flow forward through it and you get some light as a result. Nevertheless, since they are diodes, they can allow an infinite amount of current to flow (which in practice means a lot of current) and this can be problematic since, as any electrical device, it cannot handle that much current. In order to prevent them to pass too much current, a current limiting circuit is required (usually implemented as a resistor in series).
When you buy an LED, you (should) get two very important parameters, the voltage drop across them (say, V_LED), and the maximum continuous current (I_LED).
So, for the trivial case where we have a battery (V_bat) in series with a resistor (R) and an LED, the value of R must obey the following inequation:
If you decide to place many (say, n) LEDs in series, the inequation becomes:
Finally, if the LEDs are in parallel (as is the case for the repulsor), the inequation becomes:
This result can be obtained by applying Ohm’s law (V= RI) to the circuits described above. The proof is of course let as an exercise for the reader . This page has a very nice LED calculator which makes life really easy when calculating resistor values: alan-parekh.com/led_resistor_calculator.html
WARNING: the repulsor circuit may cause the LEDs to fail sooner or later. I’ll post an update as soon as I have one. Thanks to Tim for the hint.
For those interested in the repulsor circuit, below you can find a diagram describing it. It is the same as the circuit with many LEDs in parallel but with a potentiometer added to regulate the light intensity. The only requisite for the potentiometer is to be large enough to attain the dimmest light according to your needs.
I was lucky enough to help my friend Stephen and his team to build a lunar excavator to participate in the Regolith Excavation Challenge, sponsored by NASA.
We put lots of efforts and many hours to get the robot done in time and we managed to get it running before it had to be shipped to California (from McGill University in Montreal).
Unfortunately, despite the awesomeness of the lunar excavator and the fact that it was going to completely own the challenge, the UPS shipment went wrong and the robot could net get to the competition on time. Now the fight with UPS has begun to get a full reimbursement (~2000$) and the robot back.
UPS incompetence aside, I worked in putting all the electronics system together in the electrical box. This meant, I had to build two boards: one for the power management (transforming the provided 24V into a 12 and 5V in order to power the many devices and turning the latter ON and OFF), and one for the logic (interfacing the main computer with the various motor controllers and sensors).
This task was done using perfboards and lots of solder since we did not have enough time to consider designing and fabricating proper PCBs with nice places for all the components.
Note the nice (and very classy) wood finish of the electrical box interior as shown in the picture.
I will not give away any details about the excavator since it will compete next year, provided there is another Regolith Challenge.
When I saw the new Iron Man movie, I instantly knew I had to build some part of the suit (I like to wear gadgets). Luckily for me, I found an old hard drive that had just the pieces I needed for building a repulsor-like LED flashlight.
(This picture comes from IDontLikeYouInThatWay.com)
Objective
To build a very powerful LED flashlight mounted on my hand palm that would turn on and produce brighter light as I move my hand back (and the angle between my hand and my arm decreases and gets roughly to 90°). Also, the flashlight should be comfortable, allow my hand to move freely, be very sturdy, and of course look as much as possible like the repulsor Tony Starks wears on the picture above.
For those who have not guessed yet, this is what I was building.
Materials
An old (aluminum) heat sink (from a broken computer monitor I believe)
A long and thin aluminum piece from a copy machine
A street cleaner brush bristle (like the one used to build a Bogota Rake)
An aluminum disk and a thick aluminum ring (they were the holder and separator for the plates on a very old hard drive)
6 5 mm and one 10 mm ultra bright LEDs
A linear potentiometer (from an old sound system equalizer)
A switch
An old laptop battery
Some cable, some female and male headers, heat shrink tubbing, a paperclip, a plastic cable tie, and lots of love.
How to do it
Since my materials are pretty specific and it is quite unlikely that some reader may get the exact same set of materials, I won’t give a detailed description of how it is built, but rather how I did some of the key parts of this contraption.
Shaping and shining the metal:
Since the heat sinks and the other peace of metal I found were not flat (they had many 90° bends) I hammered them on a piece of thick steel until they became perfectly flat. Then, they were sanded with a fine sand paper and polisher until they where nice and shiny with some tell wool (the kind used for cleaning). I always sand and rub the metal along the same direction so it gets a consistent brushed look .
I bent the metal with my hand and worked the bends with a heavy steel rod so they are round and smooth instead of straight edges.
Linking the hand and wrist pieces:
The wrist and hand pieces are linked together bu a street cleaner brush bristle. The bristle is bent in a “Z” shape and goes into a hole at center top of the hand piece. The other end of the bristle is slightly bent upwards (so it doesn’t go into my arm when I move my hand) and goes trough a wire tie loop on the top of the wrist. A paper clip is soldered into this end and is connected to the linear potentiometer. The I heated and Inserted the clip into the plastic potentiometer tab, this creates a nice and strong link. The paperclip provides flexibility and allows the and to move beyond the range of motion of the potentiometer.
I’m very proud of this link since it is flexible, robust, and is rather easy to build.
Light:
I used seven LEDs connected in parallel (since they have roughly the same voltage and current needs). They fit nicely into the seven holes in my metal disk. In order to avoid the LED leads to short when in contact with the metal, I applied a thick layer of transparent nail polish to the metal plate previous to inserting the LEDs. The nail polish works very well as an insulator and is, for all practical purposes, invisible.
The LEDs are connected in series to the potentiometer which in turn is connected to a regular resistor. The regular resistor is used to limit the current and set the appropriate voltage for the LEDs and the potentiometer determines the light intensity. You can determine the appropriate value for the resistor by using this LED calculator.
I hope you enjoyed the information and you like the end result.
Below is a video of the repulsor beam. I know it lacks the repulsive action but still, I think it looks nice. Enjoy.
After making the electrical connections, the switch and LED(s) have to be mounted to the box by drilling appropriate holes.
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