Timeline for Ripple when switching on MOSFETs with PWM
Current License: CC BY-SA 3.0
14 events
| when toggle format | what | by | license | comment | |
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| Mar 13, 2017 at 19:52 | vote | accept | Nick Sarantinoudis | ||
| Mar 2, 2017 at 19:03 | comment | added | Nick Sarantinoudis | @rioraxe Probably yes they are wirewound. I'll look them up in the internet because they were given to me and not bought now so I'm not 100% sure of it. However your solution seems pretty easy to test. Tommorow morning I'll inform you of the results. | |
| Mar 2, 2017 at 18:59 | comment | added | Nick Sarantinoudis | @Tut I know that when turning of Arduino i will defaul to ON and I have thought to place an emergency button between the mosfets and the 12V and only start the system when arduino is properly on. Your solution seems nice, will be next try if nothing else works. | |
| Mar 2, 2017 at 18:55 | comment | added | Nick Sarantinoudis | @EnricBlanco Yes the grounds are not connected because they are different. Please read the above comment. The switching frequency is the default arduino at 490 Hz. I'll try to provide you a more detailed schematic tommorow, but i can tell you that i do have a long wire (~1 meter) to the resistors bank (R2) due to the temperature they rise in order to have them away from other electronics. Also I use some aligator clips in wires for the test and a breadboard to set up the components. | |
| Mar 2, 2017 at 18:47 | comment | added | Nick Sarantinoudis | The arduino is powered by a computer in the test setup, but in the end it will have its own power supply in order to work in every condition. The supplies are different and so they don't have a common ground. At 46 V we have a hydrogen fuel cell that provides 46 to 32 Volts depending the power needed. So 12V come from a battery in order to always have them as stable as you can. @JImDearden | |
| Mar 2, 2017 at 4:01 | comment | added | rioraxe | The load resistors you are using could be wirewound type with inductance. Putting a flyback diode across the load resistors may clamp most of the overshoot and ringing. | |
| Mar 1, 2017 at 21:09 | answer | added | bobflux | timeline score: 0 | |
| Mar 1, 2017 at 21:00 | comment | added | Tut | Your MOSFET defaults to ON when the opto/Arduino is turned OFF. Is that what you want? I would suggest moving the emitter of the opto to the gate of the MOSFET, removing R1 and connecting the opto collector direct to +12V (don't forget the ground connection others have mentioned). This will invert your PWM so you may want to rewire the LED side of the opto to turn on when the PWM pin is low. This change will actively turn-on your MOSFET, but will slow-down the passive turn-off (push-pull better as has been mentioned). | |
| Mar 1, 2017 at 20:40 | answer | added | Sclrx | timeline score: 0 | |
| Mar 1, 2017 at 20:20 | comment | added | Christian | Try adding a resistor 10 Ohm just before the gate. This looks like ringing to me. | |
| Mar 1, 2017 at 20:19 | comment | added | Enric Blanco | Are the grounds for the 46V and the 12V source connected together? They don't look connected to me. Also: what's the switching frequency and how are things wired together? Long wires may result in inductances that leads to behaviours like those seen in your scope trace. | |
| Mar 1, 2017 at 20:19 | comment | added | JIm Dearden | Could you put up a complete circuit and not leave important bits out like how the arduino is powered and the common grounding of supplies. | |
| Mar 1, 2017 at 20:09 | review | First posts | |||
| Mar 1, 2017 at 20:11 | |||||
| Mar 1, 2017 at 19:58 | history | asked | Nick Sarantinoudis | CC BY-SA 3.0 |