Battery Monitor for RoboQuadPosted by GWJax on Wednesday, 9 January 2008
This is my first mod for the RoboQuad: a battery monitor. When properly adjusted, it will visually tell you when your batteries are geting low. This mod stays on at all times. The drain on the batteries is very minute; it's around 0.02uA. This mod requires soldering and making a circuit board for the monitor, but it is a very easy circuit to build.
NOTE: If you do not understand soldering and reading schematics, find someone to help you build it or don’t attempt this mod.
So, lets get started! First, let's build the board. In this picture is the schematic for the monitor. Notice that there really aren't many parts. All parts can be substituted with like parts.
For the LED, I used a blinking LED; I thought it would look cooler than just a steady light. The list of parts are as follows: R1,R2 – 100 ohm resistor ¼ watt; R3 – mini 10K Variable resistor; D1 – 1N4733A 5.1 Zener Diode or any 4.3 to 5.1 ZD; D2 – LED (any color; I used a red blinking one); Q1 – 2N3904 or 2N2222 NPN general purpose transistor. Misc : wire, solder, soldering board, wire clippers, etc.
As you can see, it's small. The wires that have tie straps on them are as follows: red and green are for the LED and red and black are for the battery connection @ 6V. As a reminder, this circuit is designed to run even when RoboQuad is turned off. It functions as a reminder; if you shelf it for a long time, you can see that you did not take his batteries out of him. Once you have built the circuit, it is time to test it out. Attach the power to an adjustable power source and set it to 6 volts and attach the power and the ground to the circuit. If all goes well, your LED should light or blink whichever LED you put in. If it does not light, move the VR "R3" all the way to the right and then to the left and check the LED for light. If there is no light, you can recheck your wiring. Now that your LED is on, adjust your power to, or around, 3.26V; this is the threshold you want before changing or replacing your batteries. Now, adjust the VR until the light turns out. Your adjustments are complete. Lock down the VR "R3" with some hot glue so that it won't turn. You should not have to make this adjustment again. Now that you have made the adjustments, it's time to cover the circuit from any damage or shorting out. If you made the PCB the same size that I have, which is from the hole count on the board 10x9 at the cut, place a piece of heatshrink tube 1" size over it and heat it down over the circuit.
Note: make sure that you have no bad or cold solder joints before you do this.
Now, let's drill the hole for the LED; you can pick any spot that you want, but I put mine next to the left of the switch. Use a 3/16" drill bit and you may need to open the hole just a little bit for a good tight fit.
Next, trial fit your LED. If it won't go in, open the hole a little bit more.
Don't worry about that switch that you see in the photo, I was doing 2 mods at the same time. If your LED fits tightly, then you won't have to hot glue it down. I made it like this so the LED and body can be easily removed. Next comes the attaching of the power lines; how you do this is up to you. You can attach the red 6 volt line to the connector of the battery; or, you could attach it like I did by cutting the orange wire on J1 of the main circuit board connector and the black wire "Ground" also on J1, and the wire is black also. The red wire on J1 is your 3V power line; we will not be using this one, so don't cut it. Once cutting and soldering is complete, make sure you heat shrink the wires or electrical tape them.
The next step is to secure your battery monitor mod board. I placed it behind the back right motor (it fits like a glove in that position) and hotglued it down.
The only thing left is to secure and tuck away the wires. Use tie straps to hold the wires togeather and tuck them under the cavity where the back LED is located, then guide the wires from the circuit down the side of the motor. Be sure not to cover any of the screw holes. Once this is done, reassemble your Quad and install the batteries. When the LED no longer blinks or lights, the batteries need replacement.
I will post a video when my RoboQuad is back together. I hope that this mod helps you determine when you need to replace the batteries, and also as a reminder to take them out when storing it. I am looking foward to sharing more of my mods and hacks with everyone. Until then, enjoy!