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HI MATT!!! key: ☻ this color means you answered it for us!! ☻ this color means question is pending from before ☻ this color means we have a new question!! General Digi-Key Component Parameters * What’s the best DIP packages/cases (8, 10, 12, 16, etc)? ANS: There are no best DIP packages/cases to worry about. As a hobbyist/student DIP packages are the easiest to work with because they are well suited for wire wrapping and prototyping/bread-boarding. DIP chip sockets are are available at places like Radio Shack and digikey. Sockets are used to all you to wire wrap to the socket instead of the chip, so that if the chip goes bad, you don't need to change your wiring, just the chip. In terms of the number of pins, don't worry about that. You will not be approaching any pin count that would be hard to work with. * What’s the best packaging (bulk, tube, etc)? ANS: I assume you are referring to how to order the parts. Well since you only need a limited supply, then I imagine you want a tube of parts. A tube is typically a plastic container filled with the chips. Bulk refers to many chips. Often times chips in bulk are sold in what in known as a tape reel. Machines load these reels and then place chips onto the circuit boards. PWM There are 2 types of PWMs: 1) 12v PWM 2) 9.7v – 18v PWM * Is there enough output from the PWM to power the FET?? How much output voltage is needed from the PWM? I need to look up the parts and get back to you on it. DC to DC CONVERTERS * Do we want IC or power supply buck and boost converters? As of right now we have IC selected. * How many output pins are needed for each converter? It isn't really a function of how many output pins, but rather how much current the part will supply on the pin. - Do we need exactly one pin for each component? OR is it possible to feed multiple components from one output pin? Basically, the dc-dc converters produce a voltage and current. You do not need one pin per component, but rather you need to determine how much current each component will draw that uses that particular voltage. If the total current drawn by all components on that voltage rail is less than the current output of the dc-dc converter, then you are safe. If it is greater, then you need to choose a dc-dc converter with a greater current output or you will need to use multiple dc-dc converters. Personally, I don't think you will have that issue. * Does it conserve more power to keep decreasing the voltages (48 12 5) or does it matter if we use 48 5 12? In your case, I don't think it will matter. There will be a loss due to conversion in both cases and the difference, is probably minimal. Op Amp Constraints * We know we should know this… but what is the Op Amp for? Well, Op Amps have many different applications. Often times they are used to take a very small signal and amplify it. Sometimes, op-amps are used for math functions such as addition and subtraction. I would have to check your schematic to see the manner in which it is being used, but I suspect that you are taking a small signal and making it larger so that it will be detected by the processor. In other words, it is probably a small signal that needs to be translated in to a TTL level signal 0 - 5 volts. * So, is the Norton op-amp ok to use? (see below) 1) Norton Operational Amplifier – LM3900 – Single Supply of 4.5v – 32v * NOTE: This Op Amp can use either the +5v or +12 output pins 48v from Solar Panels 48v from Solar Panels DC to DC Converter DC to DC Converter +5v To PIC, D/A, RS232, OpAmp +5v DC to DC Converter +12v To PWM +12v To PWM +12v DC to DC Converter +5v To PIC, D/A, RS232, OpAmp 2) Regular Op-Amp (+/- Supply Voltage) 48v from Solar Panels DC to DC Converter +5v To PIC, D/A, RS232 +5v DC to DC Converter +10v To PWM, OpAmp -10v Diodes * Why are there 4 diodes used in the example design after the inductor….and why 2 after the voltage divider? * What is the difference between the two types of diodes the example design uses and why would one use the specific type in each location? Inductor We want a coil with the lowest possible on resistance. However, we also want to make sure we have enough inductance for when the current flows through the inductor to the diodes. We cannot find a way to understand how much inductance would be necessary for our case. Voltage Dividers * What is the resistance for the voltage dividers (what resistors)? MOSFET We know we want a FET with low resistance to prevent energy from being lost. We found a FET that has the lowest on channel resistance currently on the market (HAT2096H) * What do you think about this one? http://www.renesas.com/avs/resource/japan/eng/pdf/transistor/e2081431_hat2096h.pdf * How do we determine the ideal voltage and current of the FET? MOSFET Driver We are a little confused about what type to get since we are unsure of the voltage and current that goes with the FET PIC Software Program * Is there enough storage capacity to store EEPROM program in PIC? I need to look at the PIC, but I suspect the answer is yes. I will try to get back to you on the questions that I couldn't answer right away. Hopefully this afternoon I can get to it. If not, then I will get to it tomorrow. RS232 We are going to use the RS232 serial connection available on the PIC. With this, we will be able to closely follow the IV curve showing the output from the solar array. * Do we need to purchase any separate items for this – such as the rs232 cable to connect the PIC to the computer? MPPT Algorithm Function – Access to Solar Array Function – Access to Battery Array Function – Access to the DAC controlling the PWM LOOP: every X seconds 1. Pull instantaneous values: array output voltage (Vin) array output current (Iin) Vin Solar Array Vout MPPT Iin Iout Battery Array battery input voltage (Vout) battery input current (Iout) 2. Compare Iout to its preceding value If Iout is increasing, means Vin is approaching maximum power point. If Iout is decreasing, means Vin is leaving maximum power point. 3. Adjust Vin accordingly. Sending an appropriate voltage level to the DAC controlling the PWM can do this. 4. Record Vin and Iout Brief Algorithm Explanations Step 1: The built-in ADCs provide the PIC16F458 with 10-bit sampled values of Vin, Iin, Vout, and Iout. Step 2 & 3: The maximum power point (Vmpp) can be approached from the left (Vin < Vmpp) or from the right (Vin > Vmpp). We have to make sure that the tracker does not move Vin in the wrong direction in the process of finding maximum power point. Step 4: It is necessary to keep track of the output power trends and the movement of Vin, because it forms the basis for future adjustments to the array voltage.