Saturday, October 28, 2006, 09:49 PM
Busy last two weeks. Work included:
- Load cell testing. We drove the car wheel onto the load cell. The reading was 700 lbs. From documentation we’re thinking it should have been around 1200 lbs. We also believe some of the load might have been absorbed by the ground due to the way we had it setup. So we’ll setup a rig so the load cell is isolate better and retest.
- We did some testing on the accelerometer. After mounting the accelerometer to a board (soldering a surface mount device is hard to do) and hooking up to an amplifier we were not getting any data. After hooking it up to read none-amplified voltages it was working well. We next need to do the final wiring for this device and mounting. The 2nd accelerometer should be arriving this week.
- We built the Data Acq system stand out of PVC tubing. It suits our needs well. It will hold the CPU, all the power boxes, the command box, and the terminal breakout boxes. This Data Acq stand with all this hardware will be out at the motor test stand during the test firings.
- After initially failing we got the strain gage working (wiring configuration problem). Next step is to mount these gages onto the motor casing (once it is complete).
- We did some integration testing with the Propulsion team. They’ve been working diligently mounting our sensors (pressure, temperature, and valves). We tested 3 of the valves and they worked great. One of our solenoid valves did not work, so we mark that one not to use. This caused us to rewire one of our connectors.
We’re ready to start digging into the ignition sequence logic. This will require us to work extensively with the propulsion team to identify fault conditions and actions.
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Friday, October 13, 2006, 10:30 PM
Progress is being made. Primary highlights from today’s activities include:
- Loadcell calibration: Using LabVIEW and a set of predetermined weights we were able to determine the first order calibration coefficients. The calibration ended up being: y = 260416.66x – 120. We tested weights up to 250lbs. We will still need to test the loadcell with a much heavier load. We’ll probably lower a car onto the cell to ensure we can handle weights into the 1000’s. The loadcell can handle up to 5000lbs.
- Solid State Relay (SSR) setup: We have two devices that we have to control that used 110Vac. We are using two SSR’s that are switchable using from 4V-24Vdc. We used an old computer battery backup box and rewired it so that we can control two banks of plugs using the SSRs. All tests passed so this box is ready to go.
- Command Board testing: We did final wiring of the command board which can switch any DC power to 12 devices using 5Vdc. We are using pneumatics solenoids that require 24Vdc to actuate. We hooked up, tested, and documented all lines. The command board is ready to go.
- Terminal block hookup: We spent time hooking up all the discrete output lines which are used for commanding. Our goal is to start finalizing the terminal block wiring by end of Oct.
- Valve Block connections: We made a ribbon cable connector for our Valve Block that contains 8 solenoids. From our initial attempt we realized we misaligned the ribbon cable so we had to remake it. Second attempt succeeded. We met with the propulsion team to determine final valve configuration. Turns out we only need to use 5 of the 8 solenoid valves. We’ll finish wiring this up next week.
Problems encountered:
- Part of our power supply died today. We use 3 power supplies: a 28V, 20V, and a used PC power supply that provides 5V and 12V. The PC power supply stopped working. After debugging it turns out the fuse blew. We’ll replace that and should be operational quickly.
Coming up in the next few weeks:
- Wiring to Valves and Sensors
- Count down/Ignition LabVIEW logic
- Failure/Redline/Failsafe logic
- Test Procedures
- Closed loop control logic for main valve opening. Propulsion team is wanting to open the main valve over a 2 second period. Currently once we actuate the valve it opens in less then 100 msec. So some control logic is warrented.
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Saturday, September 23, 2006, 09:02 PM
Saturday was a great workday for the Computer team. We set out and accomplished the following:
Load Cell hookup and testing
o We made a connector for the load cell out of Bondo. (New matting connectors cost $15 each, so we went the Bondo route)
o We were able to hookup and read data, it was noisy data but when applying pressure to the load cell we did see the data change. We need to do further testing next week. We will use preset weights (10, 25, 50lbs) so that we will know what weight is applied and finish off the testing of that sensor
o With respect to the noise we were seeing, we're probably going to have to play a lot more with the filters and learn how to get rid of some of that ratty data. That should be a nice challenge.
Setup computers
o We tried to activate the new LabVIEW 8.2... but since we don't have internet connection it looks like we may have to do it manually by calling National Instruments for the activation code. In the mean time we can continue to use LabView 8.0
o We moved one data acq card to the other computer so we can use two computers for sensor testing. Later we will move that card back into our single data acq machine
Ignitor testing
o We hooked up the ignitor and were able to successfully actuate the 2 valves and the ignition spark via the high voltage source. At first there was a short somewhere and luckily we tracked it down to some of our other 'unused' wires. They were touching each other causing the short in the system, we learned some good debugging techniques.
o We did a lot of testing with the ignitor but we're going to have to do more. It must be 100% reliable
Pneumatic Solenoid testing
o We hooked up a solenoid 'switch' that allows us to apply Pneumatic pressure to a device. Looks like we may be going with valves that are actuated via pneumatics. We'll used 12 or 24Vdc to energize a solenoid that will pass air pressure to a valve which will turn the valves on, removing energy from the solenoid will cause the air pressure to be purged.
o We were successful in controlling the solenoid. We now have to wait until the final valves are acquired and determine how to control them.
Our new team members spent time learning about LabView, this will continue over the next month.
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