Posted: 6/13/2013 1:54:17 PM EDT
I am in need of a board that is no longer made. I have received the layout from the creator, but not too familiar with it (this will be my first diy board). Can anyone please tell me what resistors are needed to complete this board (red box)? Any help will be appreciated. Thank you. ETA: This is the complete board  Here are all the components:  |
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Quoted: R1 is a 100K resistor. R2 may be also. It is unclear. The resistors appear to create a voltage divider between the MOSFET source and ground. It's a power booster for a 3D Printer Extruder Controller to bump the MOSFET from 5A to 20A. Does the wattage and/or tolerance on the R1 resistor matter? The creator is in Turkey and with the current events over there, I don't want to bother him. |
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Ignore what I wrote earlier about the voltage divider. Your second diagram clarifies thing a little and I was reading the pinout of the MOSFET backwards.
Wattage and precision of the resistors is probably not going to be important in this application. I am still uncertain about the value of R2. I will try to look at it again later this evening when I have more time. |
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Quoted: Ignore what I wrote earlier about the voltage divider. Your second diagram clarifies thing a little and I was reading the pinout of the MOSFET backwards. Wattage and precision of the resistors is probably not going to be important in this application. I am still uncertain about the value of R2. I will try to look at it again later this evening when I have more time. Thanks! |
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Quoted:
Quoted:
R1 is a 100K resistor. R2 may be also. It is unclear. "10r" would probably be 10 ohm. I am going to go with 10 ohm also. It seem that it is an European standard to substitute r when the Greek letter Omega is unavailable. ETA: My apologies for not replying sooner. I was unable to log in to arfcom after the system changes last night. It was only resolved a few minutes ago. |
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Ok, I just refreshed my memory on MOSFET design as I am a bit rusty. Actually, I am feeling a bit old because I just realized that it has been around 20 years since I have done any serious analog design.
10 ohms would make sense for the gate resistor (R2). The designer probably hit the app notes to find the best tradeoff in switching time and current. |
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Quoted: It is very unlikely that Radio Shack will have the MOSFET. Try Mouser or Digikey. Those are links for the TO220 case style. That is the most likely, but not being able to the the heat sink, one cannot be certain. I called Radio Shack and they do not carry the MOSFET. I will order from Digikey. Thanks again. |