Week 4

So on Saturday I was catching a few waves with an 8'2" longboard, and I thought that wasn't too bad. Come Sunday, I was feeling more confident (aka cocky), and so I went for a 6'4" fish. I caught nothing. And the one time I did, I nosedived. Stick with the longer board, son.



This past week has been quite interesting; I feel I've been working with sensors of sorts. The test for the second heat plate went well. This time we went for a peak of about 130 degrees C. I also tested one of LM35s to measure temperature, which went well. The LM35 give you a voltage readout, which converts directly to temperature (e.g. 0.31V ~ 31 degrees C).

I got the cheap temperature controller working as well. I hotwired it with the head of an old extension cord. The only thing about this controller is that it is not compatible with the LM35, so I used a K thermocouple to test it out. I also connected it to an opto-isolator, which isolates the circuit of heating resistors and temperature controller, so the temp controller doesn't suddenly receive too much voltage and explode. I'm currently working to integrate a triac into this circuit as well. A triac is essentialy a poor-man's solid-state relay. Supposedly, it can handle up to 15 amps, and we only need 8 amps. So far, I've attached it to a comically large heat sink.

The amateur thing of the week I did was confuse the triac and the LM35. They look identical, but are obviously not the same thing. So while trying to get a temperature readout of what I thought was an LM35, I ended up frying a triac. It actually started smoking. That's when I figured I should cut the power.

Unrelated to this project, I have also learned how strain gauges work this week. After lab, I'd head down to the SAE shop to help our chief engineer attach strain gauges to the A-arms of car 46 to get some suspension data (i.e. the compression and tension on the steel members). Strain gauges measure the strain on an object by measuring a change in resistance, just like the LM35 temperature sensors. This way we can get more accurate data and confirmation on the load experienced by the suspension arms. We've also managed to get our hands on a pretty expensive data logger, so we could start attaching temperature sensors on the tires (to measure dynamic camber), speed sensors on the hubs (to measure wheel slip), position sensors, and sensors of all sorts! So next time we go out testing, we can actually get some hard numbers to backup our design objectives.

Anyway, this past week has been pretty neat. I also started to play around with EagleCAD, so I could maybe draw up a simple schematic of the whole heatplate+temperature controller+LM35 setup. Now I'm going to go figure out how to use this triac, and hopefully keep my eyebrows.