In my neck of the woods I can drive and pick it up from a local store, while buying a whole lot of other stuff I need for other projects and repairs. I can easily drop $50 - $100 every time I enter that store just to make purchasing that $0.65 item worth the trip.

 

In my neck of the woods I can drive and pick it up from a local store, while buying a whole lot of other stuff I need for other projects and repairs. I can easily drop $50 - $100 every time I enter that store just to make purchasing that $0.65 item worth the trip.

whats the local store name you go to? Is it in USA?

 

whats the local store name you go to? Is it in USA?

No. It is not in USA.

 

I don't see how you came to that conclusion. You can build a 100 mA constant current source without using a summing amplifier.

View attachment 360763

Its not working how come? Voltage across R1 is not 1.25V? Attached Draft1.asc.

 

If you want 100 mA output, try R1 = 12.5 Ω

 

If you want 100 mA output, try R1 = 12.5 Ω

Well the voltage drop has to be 1.25V across R1 regardless. I am not getting 1.25V across R1 in simulation.

 

Well the voltage drop has to be 1.25V across R1 regardless. I am not getting 1.25V across R1 in simulation.

If you want people to try to reproduce your results, you need to include the symbol and model for the LM317 that you are using.

 

If you want people to try to reproduce your results, you need to include the symbol and model for the LM317 that you are using.

Sorry see attached.

 

The subcircuit file says that it was copied from Circuitmaker Student. So I have no idea where it originated, but it seems to be a bad model.

The LM317 is the old designation for the LT317A, which is built into LTSpice. Just use that.

Also, what is it you are trying to achieve? Your circuit is not what would normally be used to achieve a constant voltage source. Are you trying to get a constant current through R1?

Playing around with the original schematic, my best guess is that the model has the pins assigned in a different order. The one that seems to make the most sense is

Pin 1: Vin
Pin 2: Vadj
Pin 3: Vout

 

The subcircuit file says that it was copied from Circuitmaker Student. So I have no idea where it originated, but it seems to be a bad model.

The LM317 is the old designation for the LT317A, which is built into LTSpice. Just use that.

Also, what is it you are trying to achieve? Your circuit is not what would normally be used to achieve a constant voltage source. Are you trying to get a constant current through R1?

By mistake i copied this cersion over the oroginal one. Where can I get the corrected version? Trying to achieve battery charger circuit.

 

By mistake i copied this cersion over the oroginal one. Where can I get the corrected version? Trying to achieve battery charger circuit.

Again, the LT317A (which is the same as the LM317 except with tighter tolerances) is built into LTSpice. Just use it.

https://www.analog.com/media/en/technical-documentation/data-sheets/lt0117.pdf

 

Any where cheap I can get LM317?

Up to Jan 8 you can buy it here with free delivery:

 

Any where cheap I can get LM317?

Where are you located? Amazon or if ordering directly from China there are AliExpress, LCSC, Temu...
btw. one can use any other voltage regulator as well. nothing stops you from using 7805 for example but since this is 5V regulator, resistor will need to be recalculated (5V / 0.1A = 50 Ohm). but you will want to stick with something that has low output. LM317 output is 1.25V. That is not the lowest voltage one can get but, this regulator is common and 1.25V is usually low enough.

 

Where are you located? Amazon or if ordering directly from China there are AliExpress, LCSC, Temu...
btw. one can use any other voltage regulator as well. nothing stops you from using 7805 for example but since this is 5V regulator, resistor will need to be recalculated (5V / 0.1A = 50 Ohm). but you will want to stick with something that has low output. LM317 output is 1.25V. That is not the lowest voltage one can get but, this regulator is common and 1.25V is usually low enough.

us but what the cheapest one. I like the lower the reference voltage the better.

 

@hhsting
fyi.
you say "You already know that I am building circuit to turn my landscape light on and off from this forum: ambient temperature problem | All About Circuits"

nope, personaly I did not know that,