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mission:resources:picouvx [2013/06/06 10:14] – [Repository] chronomission:resources:picouvx [2023/04/19 13:26] (current) – [Constant current source chains] chrono
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 |MTBF| > 100.000H |  |MTBF| > 100.000H | 
  
-<WRAP round warning>+<WRAP round alert>
 The emitter-array's output intensity is about 274 candela, the approximate luminous flux is about 25 lumen. Although the purple glow is fascinating to watch, it can hurt your eyes. **NEVER LOOK DIRECTLY INTO THE LIGHT**, without uv-protective eye cover. The emitter-array's output intensity is about 274 candela, the approximate luminous flux is about 25 lumen. Although the purple glow is fascinating to watch, it can hurt your eyes. **NEVER LOOK DIRECTLY INTO THE LIGHT**, without uv-protective eye cover.
 </WRAP> </WRAP>
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 ** Shunt resistor calculation ** ** Shunt resistor calculation **
  
-<x 14>+<m 20>
 I_{out} = {1.25}/{R_{shunt}} = {1.25}/{62} = 0.020A I_{out} = {1.25}/{R_{shunt}} = {1.25}/{62} = 0.020A
-</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,LED). 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,LED).
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 Using this many LED's in a current controlled environment and a 12V power supply usually tends to result in a higher BOM count since a serial configuration will only power 3-4 LED's per chain. One alternative would be to use a parallel configuration, which is strongly discouraged, as there is no control over the LED's internal resistance and therefore the current flowing through it. Using this many LED's in a current controlled environment and a 12V power supply usually tends to result in a higher BOM count since a serial configuration will only power 3-4 LED's per chain. One alternative would be to use a parallel configuration, which is strongly discouraged, as there is no control over the LED's internal resistance and therefore the current flowing through it.
  
-The most efficient solution seemed to be a switch-mode step-up voltage converter, transforming 12V DC up to 42V DC, which makes a serial configuration of up to 11 LED's per chain possible. This design is based on the widely available MC34063 switch-mode controller IC you can even rip off at electronic trash sites, since it's cheap and a very popular controller in chinese electronics.+The most efficient solution seemed to be a switch-mode step-up (boost) voltage converter, transforming 12V DC up to 42V DC, which makes a serial configuration of up to 11 LED's per chain possible. This design is based on the widely available MC34063 switch-mode controller IC you can even rip off at electronic trash sites, since it's cheap and a very popular controller in chinese electronics.
 ==== Specs ==== ==== Specs ====
  
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 |Q1| BC328     | PNP Transistor                | |Q1| BC328     | PNP Transistor                |
 |Q2| IRLIZ44N  | N-Channel low-RDSon MOSFET    |            |Q2| IRLIZ44N  | N-Channel low-RDSon MOSFET    |           
 +
 +**Increasing Efficiency**
 +
 +The trick to get more than 90% efficiency out of the MC34063 seems to be a very high Q inductor (L1). At first L1 was wound on a yellow/white core came out of a broken ATX supply and achieved only about 78% efficiency. After winding a new inductor onto one of these  [[http://www.vacuumschmelze.com/en/products/cores-inductive-components/applications/cores/vitroperm-standard-types-encapsulated.html|VITROPERM cores from VAC]], it increased to 93%, which is more than just considerable. There are likely to be other high-efficiency SMPS projects to come in the future where VITROPERM cores may offer substantial benefits compared to others. Time and testing will show.
 ===== Controller ===== ===== Controller =====
  
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 <WRAP round download> <WRAP round download>
-  * **Anonymous GIT Pull**git clone [[git://apollo.open-resource.org/picouvx]]+**Anonymous GIT Pull**\\ 
 +git clone [[git://apollo.open-resource.org/picouvx]]
 </WRAP> </WRAP>
  
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 {{tag>research lab uv led pcb exposer picouvx picofab}} {{tag>research lab uv led pcb exposer picouvx picofab}}
  
-{{keywords>Apollo-NG hackerspace hacker space development makerspace fablab lab community open-resource open resource mobile hackbus}}+{{keywords>Apollo-NG hackerspace hacker space development makerspace fablab lab community open-resource open resource mobile hackbus uv led pcb exposer picouvx picofab}}
  
 ~~DISCUSSION~~ ~~DISCUSSION~~