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LCFELMv2
Low Carbon Footprint Electric Lawn Mower version 2
After 04/23/2009 We finalized the mower system. The included using a 19 inch blade instead of the 22 inch blade because it used less current to run. The safety on/off switch and pull bar safety switch we connected to the system. Another field test was done for the mower system using the 19 inch lawn mower blade and then the simulation was updated to the specs for the 19 inch blade. The charger system was finalized and tested to prove it switched between AC and PV power after three days had passed. The system was also tested to make sure that it did not switch between AC and PV power in the first 3 days. 04/23/2009 – Last Day of Lab We finalized the mower simulation and found the force needed to spin the lawn mower blade while the lawn mower is running over cement. We tested the charging system to make sure that it switched between AC power and PV power at the appropriate threshold levels. 04/16/2009 – Field Testing Mower System The circuit breakers came in today and we hooked them up to our system to find out that they did not work. We looked at the circuit breaker series again and found that they have another circuit breaker that is designed for high inrush caused by starting a motor, delay number 56. We contacted Granger and they said that this circuit breaker is a special order and would take 3 – 4 weeks to get. This is not acceptable. The lawn mower system was setup using a different circuit breaker and was able to be field tested. We started by using the trimmed Sharper Blade and noticed it did not cut the grass well because the fins were removed. The Gator Blade was installed on the lawn mower and the result was a cut similar to a gas lawn mower. The batteries only lasted 50 minutes because of the high running current to cut the grass with a 22 inch blade. We will need to look at different size lawn mower blades to see if that makes a difference in the running current. We contacted CUI Inc. to verify the current sensor operation. 04/09/2009 – Circuit Breakers and Mower System Testing It was determined that we would not be able to purchase the Airpax circuit breakers because the lead time was 6 weeks. We found that Carling Technologies has a similar line and we can get the 34 delay series locally at Granger. We tested the mower system with the Gator Blade and trimmed Sharper Blade in order to create the mower simulation for each of the blades. The current sensors were tested. Using a power resistor and a DC power supply the current could be calculated and verify the analog output from the current sensor. This data was used to produce the thresholds for the charging system code. 04/02/2009 – Testing Using Different Mower Blades We tested 4 different lawn mower blades for power consumption to spin the blade, not cutting grass: 22 inch Gator Mulcher Universal, 22 inch Universal EZ Fit, 22 inch Arnold Universal 3-in-1, and Sharper Blade with trimmed fins. Our tests showed that Gator blade consumed the least power at 497 W or 22.86V at 21.75A. We updated our mower simulation to reflect the Gator Blade. We tested the Prostar Solar Charger with AC/DC power supply. We needed to make sure that the AC/DC power supply did not output more than 15 Vdc and 7.5 amps, which our AC/DC only outputted maximum values of 14 Vdc and 5.8 amps. The relays and current sensors arrived. The relays were tested with the system. Using the relays proved successful while using the EMAC. 03/26/2009 – Testing Mower System The motor and blade were attached to the lawn mower frame. We tested the system using the 22 inch Sharper Blade and found the running current to spin the blade only was 35.08 amps. This is unacceptable. We were assuming that the running current would be 18 amps or less. We believe that this is happening because the Sharper Blade is a mulching blade and it has a significant resistance due to the moving the air. We started to look for possibilities to sense when the batteries are charged. The status leds on the pro-star 15 output 1.8V when they are on. The green charged led pulses when the batteries are charged. Determining when this led is flashing could be used to sense when the batteries are charged. 03/19/2009 – No Lab Due to Spring Break 03/12/2009 – Updating Simulation and Circuit Breaker Consideration Our simulation was not correct for finding the inrush current because we did not factor in the IR losses that the lead acid batteries introduce into our system. We added the added the IR losses of our batteries into our system and found the new inrush current. With this new inrush current we searched for a DC circuit breaker that has a time delay for a high inrush current. Currently, we are looking at the Airpax APL series. The charging system code had some minor glitches. This error was fixed by complimenting out the "battery charged?" code. Since the battery is not able to be checked the system was having problems with this section of code. 03/05/2009 - Simulation for Lawn Mower We talked with Dr. Huggins and Mr. Mattus to make sure that the rest our parts are ordered. We have decided to use a Sharper Blade, extremely strong Aerospace-grade polymer, due to its ability to flex and not put the torque on the motor shaft. Once the motor blade was picked, we were able to find the mass moment of inertia of the mower blade and blade assembly. The mass moment of inertia was added to our motor simulation to find our inrush current, so we can find select the proper protection system for our lawn mower. We started to make a second version of our charger code to let the system switch back to PV power after AC power has been initiated. This will allow us to achieve a lower carbon footprint. We checked the outputs available from the PV at different light levels. It was decided that a dummy load will be used for the PV circuit so the current can be tested at all times even when the charging system is using AC. 02/26/2009 – Motor Testing with a Load The static friction and viscous friction were calculated for our motor with the prony break applied to the motor. We updated our motor simulation to reflect the motor and prony break with no load. The loaded motor simulation was compared with our loaded experimental data and our loaded simulation was within 2.5% of our loaded experimental data. We tested the code for the charging system version 1. The system will now switch to AC power after 3 days once the PV does not provide enough current. 02/19/2009 - Loaded Motor A prony break was applied to our motor and we applied different loads on our motor. These loads we will be converted to N*m and added into our simulation. We presented our progress report to our advisors and we are on schedule to complete our project on time. The final code for version 1 charging system has been completed and ready is for testing. 02/12/2009 - Motor Characteristic Testing and Simulation There was concern about the time constant and mass moment of inertia so we recalculated these values. We also found the inductance of the motor to get our final motor characteristics. These motor characteristic values were put into Matlab and a simulation of our motor, a controls class is suggested before trying to create the simulation. It was determined that our motor simulation was within 2% of our experimental values. We have the charging code version 1 almost completed. The A/D code is the one portion not complete. The A/D code will be used to check the current through the PV relay. 02/05/2009 - Motor Characteristic Testing We started the characteristic testing for our motor because our Scott 1 HP Motor did not have a data sheet. We found Ra, Kt, Kv, Ts.f., b, and J for our motor. Based on our values, our simulation of the motor is going to be within 2% of our experimental data. We also completed the programming for our PV charging system. Our goal is to have out microcontroller timing to be a few minutes of actual time after 4 days. We completed the stop module for the charging system. The clock was checked for accuracy and after ten minutes the time was still correct. 01/29/2009 - Motor Testing Begins Our motor arrived and a testing platform was created. We started no load testing using the DC Power supply in the Power Lab. We also tried to capture the inrush current using the DC power supply and found that the current was being limited by the DC power supply. We connected the Motor to the 2 - 12 volt batteries, which broke the current shunt because the inrush current was more than 35 Amps. (Update: The no load data was not accurate because the motor was cold and the tape on the motor shaft was not setup correctly.) We started to make the code for the charging system. The main and timer modules were completed. 01/22/2009 - Official Launch of Website We were excited to launch the website for our project. This website will be updated weekly.