Differences
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| Both sides previous revisionPrevious revision | |||
| mission:resources:picouvx [2016-03-18 08:37] – [BOM] chrono | mission:resources:picouvx [2023-04-19 13:26] (current) – [Constant current source chains] chrono | ||
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| ** Shunt resistor calculation ** | ** Shunt resistor calculation ** | ||
| - | <x 14> | + | <m 20> |
| I_{out} = {1.25}/ | I_{out} = {1.25}/ | ||
| - | </x> | + | </m> |
| Combining an LM317 and a 62 Ohm shunt resistor regulates the current flow to 20mA per chain, running the LED's at their typical recommended operational forward current to maximize the lifespan but leaves room to increase the current if exposure times need to be shorter. If you don't have 62 ohm resistors on site, just use 68 ohm (18mA per chain). The input voltage must be at least 3,5V + sum(Uf,LED) (Uf=Forward Voltage, | Combining an LM317 and a 62 Ohm shunt resistor regulates the current flow to 20mA per chain, running the LED's at their typical recommended operational forward current to maximize the lifespan but leaves room to increase the current if exposure times need to be shorter. If you don't have 62 ohm resistors on site, just use 68 ohm (18mA per chain). The input voltage must be at least 3,5V + sum(Uf,LED) (Uf=Forward Voltage, | ||