Timeline for How to achieve constant current around 325mA for a 1W power LED with low headroom voltage
Current License: CC BY-SA 4.0
6 events
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| Feb 2, 2022 at 10:30 | comment | added | tobalt | @MarkHightonRidley Thanks for reporting back! I wish many more people did that :) Usually, people only return if things don't work out as planned. | |
| Feb 2, 2022 at 9:45 | comment | added | Mark Highton Ridley | Thanks for your guidance @tobalt and hacktastical. I've now got a properly working circuit. I used a MCP6021 PDIP package op amp (perfect for stripboards) and an IRLB8721 MOSFET. For the reference voltage I used a resistor divider (150kΩ and 1.2kΩ). | |
| Jan 25, 2022 at 15:32 | comment | added | tobalt | @MarkHightonRidley also use a MOSFET with low enough turn on voltage. so that you can turn it on with the available output swing of the opamp. Basically just use a rail-to-rail input-output opamp and MOSFET with maximum of around 2.5V gate threshold voltage. As you have spice, you can check how different MOSFET will cope. | |
| Jan 25, 2022 at 15:29 | comment | added | Mark Highton Ridley | Thanks, @tobalt, itlooks like it will do as I want. I'll get hold of an appropriate op amp as suggested and give it a try. I still would like to know how to adjust the original circuit for my own learning :) | |
| Jan 25, 2022 at 15:26 | history | edited | tobalt | CC BY-SA 4.0 |
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| Jan 25, 2022 at 15:19 | history | answered | tobalt | CC BY-SA 4.0 |