Hi
I have been doing some circuit analysis on this and bench testing with various loads and with different R values and Zener values.
Because the load of the Arduino varies depending upon what it is doing, from pretty much nothing to at least 100mA, this causes a variation in the voltage going to VIN. And can result in the resistor and zener getting hot.
To stablize the voltage to VIN, its probably best to use a voltage regulator such as LM7808. Using a TO-220 package means being able to use a heatsink to dissipate any heat. There is no way the Nano will draw anything close to the current limit of the LM7808 so thats a better choice.
I will modify all the circuits and docs and layouts (stripboard and PCB) and parts lists etc so that going forward, the LM7808 is the preferred choice. The circuit is earlier in this post. Changes will take some time to do, but no changes necessary in firmware or applications or drivers.
Cheers
Robert
Last edit: brownrb 2016-09-30
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Hi
I have been doing some circuit analysis on this and bench testing with various loads and with different R values and Zener values.
Because the load of the Arduino varies depending upon what it is doing, from pretty much nothing to at least 100mA, this causes a variation in the voltage going to VIN. And can result in the resistor and zener getting hot.
To stablize the voltage to VIN, its probably best to use a voltage regulator such as LM7808. Using a TO-220 package means being able to use a heatsink to dissipate any heat. There is no way the Nano will draw anything close to the current limit of the LM7808 so thats a better choice.
I will modify all the circuits and docs and layouts (stripboard and PCB) and parts lists etc so that going forward, the LM7808 is the preferred choice. The circuit is earlier in this post. Changes will take some time to do, but no changes necessary in firmware or applications or drivers.
Cheers
Robert
Last edit: brownrb 2016-09-30
All new changes re LM7808 made and uploaded.
Last edit: brownrb 2016-09-30