| ??? 03/21/05 16:14 Read: times |
#90139 - Freewheeing Diode Responding to: ???'s previous message |
Juan Carlos said:
Steve I do not have that. I will find info about it and try it. What would it be doing?J.C. When the FET turns off, the magnetic field in the solenoid collapses and creates a large back emf voltage which can damage the FET and anything else connected to the solenoid. The magnitude of the back emf is given by -Ldi/dt where L is the inductance of the solenoid and di/dt is the rate of change of current which can be a very large value if the FET switches off in a microsecond or so. The negative sign indicaes the voltage produced is in a direction that tries to counter the current that caused it. So if you put a diode across the solenoid with its cathode to the positve end it will reduce the back emf to a diode forward voltage drop. It is essential you use such a diode when driving a solenoid and it needs to be a beefy one too. Something like a 1N5000 series. Ian |
| Topic | Author | Date |
| LPC932 Oscillating | 01/01/70 00:00 | |
| scope | 01/01/70 00:00 | |
| Scope | 01/01/70 00:00 | |
| BIG electrolytic | 01/01/70 00:00 | |
| Bypass where | 01/01/70 00:00 | |
| Diode ? | 01/01/70 00:00 | |
| No I do not | 01/01/70 00:00 | |
| flywheel diode | 01/01/70 00:00 | |
| Freewheeing Diode | 01/01/70 00:00 | |
| Holy Cow | 01/01/70 00:00 | |
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| flywheel | 01/01/70 00:00 | |
| Thank you all! | 01/01/70 00:00 | |
| Flywheel | 01/01/70 00:00 | |
| flywheel. | 01/01/70 00:00 | |
| battery | 01/01/70 00:00 | |
| Did not work | 01/01/70 00:00 | |
| try both LF and HF | 01/01/70 00:00 | |
| 3.3 amd 6.6 | 01/01/70 00:00 | |
| Thats it | 01/01/70 00:00 | |
| LM2937 | 01/01/70 00:00 | |
| what is solarbotics | 01/01/70 00:00 | |
| Excellent | 01/01/70 00:00 | |
| Battery | 01/01/70 00:00 | |
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| Diode 1N4000 | 01/01/70 00:00 | |
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| Got it. | 01/01/70 00:00 | |
| Answer needed, please | 01/01/70 00:00 | |
| Whoops! | 01/01/70 00:00 | |
| You don't know the currents?????? | 01/01/70 00:00 | |
| Current ? | 01/01/70 00:00 | |
Found out what currents are flowing? | 01/01/70 00:00 | |
| nope | 01/01/70 00:00 | |
| Ok | 01/01/70 00:00 | |
| Diode type | 01/01/70 00:00 | |
| Oscillations... | 01/01/70 00:00 | |
| aka | 01/01/70 00:00 | |
| Exactly! | 01/01/70 00:00 |