| ??? 01/27/06 13:54 Read: times |
#108501 - internal diodes Responding to: ???'s previous message |
Coils produce back EMF when they turn off. this back EMF could be damped by the ULN driver IC without any external Diode (You will need to connect the anode of internal diodes to the relays supply).
While the above is correct, I have seen cases where it still fails. If you make a simple transistor - diode - realy driver and scope it you will see dramatic differences when the diode is across the relay and when it is from the transistor to V+ and the relay is a foot or more away. SO, the internal diodes WILL protect the transistor, but the EMI will be dramatic if the realys are not VERY close. Erik |
| Topic | Author | Date |
| Relay board diagram | 01/01/70 00:00 | |
| Just search for, "Relay" !! | 01/01/70 00:00 | |
| andy Neil | 01/01/70 00:00 | |
| Relay ratings | 01/01/70 00:00 | |
| ULN2803,ULN2003 | 01/01/70 00:00 | |
| more on relay ratings | 01/01/70 00:00 | |
| Yes of course | 01/01/70 00:00 | |
| internal diodes | 01/01/70 00:00 | |
| ULN2003's doesn't easily burn | 01/01/70 00:00 | |
| Uce saturation voltage is rather high | 01/01/70 00:00 | |
| there is an alternative, search for it | 01/01/70 00:00 | |
| I agree | 01/01/70 00:00 | |
| That is bad design | 01/01/70 00:00 | |
| ULNs resist more... | 01/01/70 00:00 | |
| I would never suggest 74HC buffers for d | 01/01/70 00:00 | |
| Yes , you didn't | 01/01/70 00:00 | |
| I would like to see where that is, pleas | 01/01/70 00:00 | |
correct link | 01/01/70 00:00 | |
| Bad Design? | 01/01/70 00:00 | |
| naah | 01/01/70 00:00 | |
| Also depends on transistor speed | 01/01/70 00:00 | |
| valid issue, but not that, now another | 01/01/70 00:00 | |
| Indeed | 01/01/70 00:00 | |
| Serial | 01/01/70 00:00 | |
| How much current? | 01/01/70 00:00 | |
| allegro | 01/01/70 00:00 | |
| and infineon | 01/01/70 00:00 |