Vidim niko se nije javio na moj zadnji post ,ja sam nasao semu konkretno za ovo sto mi treba ali nisu mi jasne neke stvari.
Ovo je text sto je napisao avtor seme
Circuit Description:
I used an interface circuit – buffer and voltage summer followed by a PWM (pulse width modulation) circuit. The output of PWM circuit feeds a MOSFET driver and then a MOSFET is the final stage that drives the blower motor. There is also a snubber circuit to assist with the switching.
- Build the control circuit. You can just copy my design, or modify your own. There are a few finicky parts, so please bear with me here. You will need to use an oscilloscope to calibrate your design - this is NB. On the output stage of your cct, there should be no noise. This is critical. I tested mine even in the car while connected to battery supply, and made sure no noise. You should only see the PWM pulses on the gate of the FET with no ripple (its okay if there is ripple on the positive pulses, but none on the 0V parts.
The aircon for my vehicle had 7 settings from low to high. The voltage for each setting is shown below:
Setting 1 (lowest): 0.938V
Setting 2 : 1.13V
Setting 3 : 1.65V
Setting 4 : 2.5V
Setting 5 : 3.4V
Setting 6 : 4.31V
Setting 7 (highest) : 6.4V
Use the variable pots on the PWM stage to get your circuit to start its PWM at say 0.7V and then let it reach its max at say 6V. That is what i did and it works perfectly.
Notes:
1. I put a resistor across the gate to ground of the MOSFET. I used a 10K Ohm resistor 1/4W. I left it off the diagram by mistake. It is not mandatory.
2. My snubber circuit was a bit over kill. I am sure that just one diode would have been fine. I felt that if the aircon was set to "Hi", that means that hot air would be passing through the blower area. I was worried about too much heating in a worst case scenario. Also the capacitors across the diodes. That is personal preference. I tried with and without the caps and i found a noticeable difference in the spurious switching of the MOSFET. The caps improved the stability but added more higher peak ripple on supply line. They did reduce high dv/dt though so i left them in.
3. My circuit did not even get warm after a fair testing time. If your output MOSFET gets warm quickly, please check your driver stage as noise was one of my challenges in the design. In the end it was solved by the placement of my earth wire for the mosfet driver IC. Make sure that your earth wire is as close to the car's earth wire. An additional capacitor on the output of the MOSFET driver also helped. I used a 2.2nF and is shown on my cct diagram. If that cap is not there, you will pop your FET in about 4mins. I poped mine in 30s as it was not on a heatsink while testing the original prototype.
4. I had an issue of my blower not turning off when the aircon was set to off. This was easily fixed by calibrating the two variable resistor (Pots). You can also use a comparator cct and FET driver to control the relay cct which i will do for a future design. A kind of forced off situation.
5. The relay and smoothing cct is not mandatory.
6. The 7808 reg chip is highly recommended for stability. Owing to the fact that the input stage gets its reference from the supply voltage, changes in supply voltage would affect the OP-amp comparator. Thus i regulated mine so that when the car is on or off the response is the same from the op-amp cct.
7. I used a bit of epoxy to dampen any vibration and also to hold the cct in place. Whatever you do, try keep the clearance of the cct short as the black blower cover fits snugly. I had to shorten two cables as the space was just too little.
8. I use the term ground which means chassis, or your 0V on the car. All the same in this case.
Moja pitanja
1.Kod lm324 koji otpornik ide od 13 pin do 14 pin? jer na slici nemogu da vidim koji je posto je postavljen nagore,ovaj drugi otpornik sto ide prema A video sam na slici celog sklopa (2,2k-ohm)?
2.O cemu sluze ova dva potenciometra isto na lm324 jer covek nije dobro objasnio.
3.U jedan deo text-a pise da je on izbacio neke kondenzatore ? ili ostavio kao sto su na semi,ne mogu da razumem bas posto na slici sa plocicu vidim nedostaju neki u odnosu na seme
(I tried with and without the caps and i found a noticeable difference in the spurious switching of the MOSFET. The caps improved the stability but added more higher peak ripple on supply line. They did reduce high dv/dt though so i left them in)
4.Na sg3525 C4,C1,C3=0.01 sta? Ja mislim da je nF ? ako gresim popravite me...
HITNO MI JE!
MARK123
Regulator za brzinu ventilatora(hladjenje/grejenje)
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