General > General Discussion
Minatronics 1.5V Incandescent Bulbs
TwinStar:
Parts List; Am I on the right track?
https://www.digikey.com/product-detail/en/texas-instruments/LM317LCPK/296-26093-1-ND/2254850
https://www.digikey.com/product-detail/en/susumu/RL1220S-R82-F/RL12S.82FTR-ND/432492
https://www.digikey.com/product-detail/en/panasonic-electronic-components/ERA-3AEB161V/P160DBTR-ND/1465835
emd_16645:
--- Quote from: TwinStar on September 02, 2018, 10:50:18 PM ---Y'all should charge tuition.
--- End quote ---
I’d pay tuition for these lessons if it meant we get to see some progress on that layout of his...
G8B4Life:
--- Quote from: TwinStar on September 02, 2018, 10:50:18 PM ---Y'all should charge tuition.
--- End quote ---
Not me, I'll just end up putting my foot in it and no one wants to pay for that. I knew how a globe worked, I knew exactly what a constant current device was yet I put my foot in it by trying to be cheeky and call something what it isn't because we end up with the same desired result :-[
I did that (stupidly) because I missed Alan's link to all those wonderful SMD constant current devices (where were they 10 years ago when I wanted them?) and I have never seen or heard of anyone using a constant current device for headlights etc; I've only ever seen articles on using the LM317.
--- Quote from: TwinStar on September 02, 2018, 11:09:00 PM ---Parts List; Am I on the right track?
https://www.digikey.com/product-detail/en/texas-instruments/LM317LCPK/296-26093-1-ND/2254850
https://www.digikey.com/product-detail/en/susumu/RL1220S-R82-F/RL12S.82FTR-ND/432492
https://www.digikey.com/product-detail/en/panasonic-electronic-components/ERA-3AEB161V/P160DBTR-ND/1465835
--- End quote ---
First link, LM317 look's ok.
Second link, that's a 0.82 Ohm (820 milliohm) resistor. You need an 820 Ohm. This should do the trick: https://www.digikey.com/product-detail/en/panasonic-electronic-components/ERJ-8GEYJ821V/P820ECT-ND/203366
Third Link, power rating too low*, this should do: https://www.digikey.com/product-detail/en/panasonic-electronic-components/ERJ-8GEYJ161V/P160ECT-ND/203277
* Based on Alan's previous post stating 1/4W components.
- Tim
Alan:
You can use 1/10W resistors if you wish. There is only 1.53mA of current through the divider network at an output of 1.5V. That equals 0.0023 watts, well below 1/10th watt. I said 1/4 watt resistors only because Jacob mentioned he had on hand 1/4 watt pieces.
With SMD components there is very little size difference so doesn't matter much which you choose. The LM317 will take up the bulk of the space.
It is worth mentioning an LM317 can use an upper divider resistor of a any value between 100 ohms and 1000 ohms but it exhibits maximum stability with an upper resistor of 220 ohms (actually 240 but that value is not readily available). For a light bulb stability is not much of a concern. However, for others that want to use this circuit for something where maximum voltage stability is critical then you really should consider a 220 ohm upper resistor. Since the output voltage is a function of both resistor values, changing the upper will change the lower. It will also change the total current flowing through divider network which will determine the wattage of the resistors.
Here is a handy LM317 resistor calculator: http://www.reuk.co.uk/wordpress/electric-circuit/lm317-voltage-calculator/
Once the values have been determined then use Ohm's Law to calculate the resistor wattage: http://www.ohmslawcalculator.com/ohms-law-calculator
Remember to double the power value so your resistors run cool.
Alan:
--- Quote from: G8B4Life on September 04, 2018, 09:21:26 AM ---
Not me, I'll just end up putting my foot in it and no one wants to pay for that. I knew how a globe worked, I knew exactly what a constant current device was yet I put my foot in it by trying to be cheeky and call something what it isn't because we end up with the same desired result :-[
I did that (stupidly) because I missed Alan's link to all those wonderful SMD constant current devices (where were they 10 years ago when I wanted them?) and I have never seen or heard of anyone using a constant current device for headlights etc; I've only ever seen articles on using the LM317.
- Tim
--- End quote ---
Naw, there is no stupidity going on. It is a lively give and take discussion where we all learn. Exactly what message boards are meant to do.
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