| ??? 05/05/10 05:25 Read: times |
#175693 - 3 ohm load Responding to: ???'s previous message |
with 3ohm load You have 4A+ current. Heat will be (Rdson * 16) W.
So You should search for lowest possible (and cheap) Rdson. IRF840 in Your circuit is 0.85ohm. So You have 11..13W static power dissipation. Search for other transistor - IRF840 is high voltage type - You don't need them. 4A is really light circuit , with good parts. IRF540 has 0.077 ohm Rdson - difference is 10 times. Listed price here is 0.38euro - same as for IRF740 (840 is not listed). LM5111 has stated ON resistance of 1.5 ohm - how can be better in Your case? Primary function is MOSFET gate driver. Third in list(page one datasheet) is relay and motor driver. Dinamic power dissipation can be problem too - even on 300 Hz - with slow optocoupler edges. So think about sharpeninng and maybe some Shmidt buffer between opto and transistor. So- if You buy SSR to solve this problem - You will pay for this know-how , which You currently learn. Parts inside will be same. regards and good luck |
| Topic | Author | Date |
| high current output SSR or opto | 01/01/70 00:00 | |
| Something like this perhaps? | 01/01/70 00:00 | |
| thank you | 01/01/70 00:00 | |
| Use due care... | 01/01/70 00:00 | |
| expansion | 01/01/70 00:00 | |
| Depends | 01/01/70 00:00 | |
| I agree | 01/01/70 00:00 | |
| Bleh! | 01/01/70 00:00 | |
| I caught that... | 01/01/70 00:00 | |
| half voltage | 01/01/70 00:00 | |
| why load is there | 01/01/70 00:00 | |
| Check These Items | 01/01/70 00:00 | |
| Load Placement | 01/01/70 00:00 | |
| Load placement | 01/01/70 00:00 | |
| thank you everyone | 01/01/70 00:00 | |
| 3 ohm load | 01/01/70 00:00 | |
| good advice | 01/01/70 00:00 | |
| If I understood your requiremnt properly have a look ULN2003 | 01/01/70 00:00 | |
I don't think so | 01/01/70 00:00 |