MegaBitMeter – DIY Kit Assembly Guide
Here’s how to assemble your MegaBitMeter kit. These instructions are valid for batch 1.
Skills you should bring:
- Basic soldering skills
- Basic Arduino knowledge
You need these tools and materials:
- MegaBitMeter Kit 1 plus your own Arduino OR MegaBitMeter Kit 2
- Small Philips head screw driver
- Small flat head screw driver
- Wire cutter/stripper
- Solder and an electronics soldering iron
In case you want to install your Arduino inside the housing of the meter, which we assume, you also need this.
- Superglue or hot glue
- Xacto knife
You might also just leave the Arduino outside. If you use a longer line to detach your Arduino, you might want to use a switching transistor to protect it. That’s why we added a transistor and another resistor to the kit.
Step 1 – Remove scale
Follow the instructions on how to change theMegaBitmeter scale and remove scale completely.
Step 2 – Remove glass
Carefull remove the front frame and glass. Take care to not bend the needle.
Step 3 – Change internal resistance
The internal resistance of the meter set for 5V DC when the needle shows 1000Mbps. Depending on your Arduino, the needle might be just a bit below 1000Mbps when set to maximum value. We want to allow for a bit of calibration so we change the internal resistance of the meter. Solder one of the 10k resistors that came with the kit parallel to one of the internal 2k resistors, preferably the one soldered to red wire (important just for spacing later). It should look like this.
In case you find it difficult to solder inside the housing, you might want to remove screw holding the wire to the terminal.
Step 4 – Prepare IC socket
We’ll refrain from soldering leads directly to your Arduino’s pins. We’ll solder them to an IC socket instead, to protect your Arduino. Also, it might come handy to be able to remove it from the housing some time. Bend the legs of the IC socket to the outside. That works best by gently pushing them onto a table surface all at the same time.
Step 5 – Carve mini USB jack hole
Chose a point where you want the Arduino’s USB jack to peek out of the housing, preferably the bottom.
Aim well and carve a hole. You might want to remove the moving coil and black backplate for this. Simply remove the four screws on the back of the meter. The hole should look like this, although you can certainly do better than us:
Step 6 – Wire up the IC socket
Align the Arduino with the IC socket, so that pins TX1 and Vin are sitting in the socket. Pins D10-D13, 3V3 and Vref are free. Now find GND and the PWM pin you want your Arduino to be connected to the meter. By default, that is pin D3. Now cut two pieces of wire, two to three inches (5cm to 7.5cm) long. Strip the ends (2mm) and solder one each to D3 and GND. Solder the one attached to D3 to terminal A (marked on the back). Solder the wire attached to D3 to terminal C. Alternative: depending on your soldering skills, you might also directly solder the 2k resistor wired soldered to terminal C to D3, as shown in the picture below.
Step 7 – Insert Arduino and glue in IC socket
Step 8 – Install Software
The free and open MegaBitMeter software is available via our download page at http://megabitmeter.de/shop/downloads/. Compile and upload into your MegaBitMeter. When the Arduino inside resets, it will initially set the needle to 0, 200, 400, 600, 800, 1000 and back to 0. You can e.g. use the Arduino IDE’s serial monitor to set values. Set your connection to 9600 (8N1), send a number from 0-1000 as a string and add a newline. Voila!
$ ./devstats.pl eth0 > /dev/ttyUSB0
Using a different OS? Please contribute!
Step 9 – Calibrate!
Position 0: When your MegaBitMeter is not attached to power, calibrate the 0-position. Use a flat-head screw driver to gently and slowly turn the small black knob in the lower right corner of the meter, so the needle hits 0.
Position 1000: When your MegaBitMeter is set to maximum value via software but the needle does not quite hit 1000, you can adjust this by setting the maximum constant in the header of the Arduino software, e.g.
static float maximum = 249; // maximum value for 100% meter
Notice: Your meter is made for upright use. It’ll be fine standing upright or slightly tilted, as it is when mounted in the MegaBitMeter stand.
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