This week was not very eventful as I was only at school for two days. I continued to work on the leg, and I successfully printed a new version of the legs with the correct proportions. I also worked a little on the Mars Rover Project since the launch failed and some parts were destroyed. Continue reading Week of 3/23
This week I tested the resolution of the servo motors. I used a basic setup of a servo motor with a mirror glued to the horn and I controlled the servo using /Servo.writemicroseconds()/. First I started by decreasing the size of the pivot of the motor. Through this Test I found that the servo motor’s minimum movement is 20ms, I also found that the servo is very inconsistent at these small movements. Next I used a servo driver module, our thinking was that this module had a better internal clock than the arduino and would give more accurate movements as well as smaller steps. This was not the case the results were the same as using a servo without the driver. Finally I built a rig to test my idea of gearing down the servo motor for more precision. Here is the rig:
Basically, it is a 10:1 pulley system with the mirror mounted on the pivot point. In theory,this should increase the precision of the servo by 10x. Below is a video of the rig cycling through some angles.
With this setup I achieved my goal of 5mm precision at 0.6m.
My next goal
This week I had worked with the GPS module to see how accurate it could be I got it down to 1 ft from the goal which I can set with a seprite button. To get the distance function I had to take the adifruit parsing code and insert a distance function from a tiny GPS ++. I now have it set so that when one button is pressed it sets your goal and the other button will tell you how far away you are and if it is within 15 ft it will activate the servo to open the box.
Last week I focused on planning out and coding how the car should react in different scenarios that are recognized by the 3 sensors I added last week. The car now preforms very well and can weave through obstacles nicely. With all of this software success it wouldn’t be right for the hardware to just do its thing and keep up. the spring that pulls the front wheels straight whenever the car is not turning is busted and fails to pull the wheels together against the traction of the ground. This week I will look into upgrading to a better and larger vehicle. I will also try to find a replacement spring so I can continue development until I get an upgrade.
Once again, I continued work on the Mars Rover. This was a week of testing and more testing. We finished the week with a fully functional lander, which is go for launch on next Saturday.
This week I researched power sources for my laser system. Because a laser is a diode, it has virtually no resistance, so it will keep drawing current until it burns itself out. Because of this, the laser requires a constant-current power source. The first result of my research was a LM317 constant-current power supply circuit (shown below), this circuit is very popular amon laser pointer enthusiasts.
This is a good circuit, however it will not work for my application. The LM317 has a max operating amperage of 1.5 in a 5 volt system. This would work for a 5W laser, however my system will be using 25W, so I continued my research. My teacher recommended a 2-channel power supply from Mouser electronics supply. This power supply can deliver 40W on one channel (which is more than enough for the 25W laser) and the second channel can be used to power the arduino and servos.
Next week I will design a prototype to test having a gear ratio with the servos, and test the mirror’s efficiency with the laser.