SIMPLE DIRECT DRIVE DESULPHATOR/ DESULFATOR KIT INSTRUCTIONS

Transcription

1 SIMPLE DIRECT DRIVE DESULPHATOR/ DESULFATOR KIT INSTRUCTIONS Parts List C1 470uF/ 25V 1off C2 C5 0.1uF/ 50V 4off C6 C9 0.01uF/ 50V 4off D1 12V/ 1.3W zener 1off Q1 2N2907 1off Q2 Q4 IRFB3307 3off R1 510R/ 2W (Gr Br Br) 24V input 1off 1k/ 3W (Br B R) 36V input 1off 1k5/ 5W 48V input 1off R2 & R6 3K (O B B Br Br) 2off R3 22.6K (R R Bl R Br) 1off R4 10K (Br B O) 1off R5 100R (Br B B B Br) 1off U1 U2 LM555 2off U3 U4 TC4426 2off 8pin DIL socket M4 x 12mm brass bolt M4 brass nut M4 brass washer PCB 4off 4off 8off 8off 1off Gr = Green, Br = Brown, B = Black, R = Red, O = Orange & Bl = Blue Page 1 of 7

2 Ignore the values for R1 in this schematic they are incorrect. Page 2 of 7

3 Firstly let me give credit to Mark Lookwood aka tusconshooter for the design of this device. His original intention allowed for R2 and R6 to be 3k NTC thermistors, however with the MOSFET s being used they are not required so we supply straight forward 3k resistors to use in their place. If the end user wants to replace these with the thermistors as originally intended i.e., glued to the MOSFET heatsink, then feel free to do so. In this case as the MOSFET s get hotter the frequency of operation and pulse width will be reduced. As designed this device will work at a frequency of 2k with a pulse width of 33uS. Use a 4.7 to 100R/ 10W (or larger) rated resistor for current limiting. We don t supply a heat sink. Page 3 of 7

4 Features of the Direct Drive Building Block - Two 555 timers, one for frequency and one for pulse width. You can jumper around one of them if you only want to use a single 555 timer. - Thermistor ready. One resistor on each of the 555 timers can be replaced with an NTC thermistor to provide thermal feedback. - Uses the TC4426 MOSFET driver chip. This also can be jumpered around if you want to use your own driver circuit. - Large ground plane and filled power planes around MOSFETs and driver chips. No ringing, oscillations or extra pulses. - Large ground and output pads on both sides of the PCB. - Simplicity! The PCB has only three connections. - Small size, 2.5 by 3.8 (without heat sink.) - MOSFETs are along the edge of the PCB for mounting on a heat sink Mark s explanation of the circuitry is as follows First there are a few extra parts around U1, namely Q1, R2, R3, R4, R5. These parts are there to allow using a thermistor to keep the temperature of the MOSFETs under control. If R2 is replaced with a like resistance NTC thermistor and thermally connected to the MOSFET heat sink then as the MOSFETs get hotter, the frequency will be reduced until an equilibrium is reached between power and temperature. In other words, this circuit will keep the MOSFETs from getting too hot. If you don't care about this feature, then you can simplify the circuit by not installing R2, R3 and Q1 (jumper emitter to collector of Q1) and you will have a classic 555 timer circuit as seen in most all of the other desulphator circuits. Of course, installing all of the parts (R2 is a simple resistor) works just as well also. The second 555, U2, is triggered by U1. Using two 555 timers like this separates the frequency from the pulse width. The pulse width can be thermally controlled like the frequency of U1. If you replace R6 with a NTC thermistor of like value and thermally connect it to the heat sink then as the MOSFETs gets hotter the pulse width will go down. If you are starting to think that the extra parts are there just for temperature control of the MOSFETs, then you are right. If I did not build in that feature then the board would have been a lot simpler, and less flexible. Instructions 1. Check all the components are present. 2. Attach the M4 brass bolt c/w a nut to the points TP2/ TP3/ TP4 & TP5 and solder them to the pads both on the bottom and top of the PCB. This ensures a good solid electrical connection. Page 4 of 7

5 3. Solder the rest of the components to the board working from the smallest upwards. C1 has a broad white band marking the shorter negative leg, this should face the edge of the PCB. Solder R1 with a space between it and the PCB to allow it to breathe. 4. Short out the jumpers JP1, JP2 & JP3. Page 5 of 7

6 5. Connect Points A B, C D and E F. These are the MOSFET gate drive connections. They are done this way to maximize the copper on the PCB for current carrying. 6. You will note from the earlier schematic the end user will need to supply the mains powered input and capacitor bank to go with this circuit. 7. The end user will also need to supply the heat sink for the three MOSFET s. The MOSFET s chosen have a very low R DS value and proper MOSFET drivers are employed to drive them but there is going to be heat especially at the higher voltages. 8. Attach a M4 bolt and nut to each of TP2/ TP3/ TP4 & TP5 and then solder the bolt to the bottom of the PCB and then solder the nut to the top of the PCB. This will ensure maximum power transfer. The PCB shown above is the 36V model. Initial PCB Power up 1. Visually inspect your PCB, your interconnect wiring. Look very closely for solder bridges. Are the IC s in the right way around. Double check the parts including correct orientation of diodes and electrolytic capacitors. 2. Do not connect a battery. (Leave leads disconnected) 3. Use the highest value current limiting resistor. 4. Assuming that jumpers: JP1, JP2, JP3, AB, CD, and EF are connected and that all parts are populated. 5. Apply power, if nothing is smoking then leave power connected. Page 6 of 7

7 6. Connect the negative lead of a volt meter to TP2/ 3. All further measurements will be made with negative connect to this point. 7. Connect the meter positive lead to the positive terminal of the cap bank. You should read greater than 1.4 times your transformer secondary voltage. 8. Connect the meter positive lead to the positive side of C1 on the PCB. You should read a little over 12V. 9. R1 should be cool or slightly warm to the touch. 10. Some meters have a frequency mode. Connect to JP1. The frequency should be about 1000Hz. Alternatively get a small speaker and connect a resistor (100 to 1000R) to one lead. Connect between TP2/3 and JP1. You should hear a tone. 11. Connect meter/speaker to JP2. Tone should be "harsher". 12. Connect meter/speaker to JP3. Tone should be much louder and harsher. 13. Disconnect speaker from TP2/3. Connect speaker (both leads) in place of the battery for a very short time. Should be very very loud. 14. Power off and connect battery. You are ready to ROCK!!!!! 15. As you reduce the resistance of your limiting resistor, your peak current will go up. Check for hot parts as you increase current. Troubleshooting 1. Remove all of the ICs. Measure voltage across D1 (Zener diode). Should read 12V. If still low then check out your PCB for shorts. Check D1. 2. If voltage above is OK then install U1. Check voltage across D1. Scope pin 3 (U1). You should see about 1KHz pulse. 3. If pulse is OK then install U2. Check voltage across D1. Scope pin 3 (U2). You should see about 1KHz pulse rate at about 10uS wide. 4. If pulse is OK then install U3. Check voltage across D1. Scope pin 7 (U3). You should see about 1KHz pulse rate at about 10uS wide inverted. 5. Scope pin 5 (U3). You should see about 1KHz pulse rate at about 10uS wide not inverted. 6. Install U4. Check voltage across D1. Scope pin 7 (U4). You should see about 1KHz pulse rate at about 10uS wide not inverted. Page 7 of 7