Question about a circuit

[ShadeTreeMechanic]

You should be able to put a high value resistor in series with it. Like a 10k ohm. A pot would work if set up as a voltage divider but is not necessary to light the led.
If you wanted exactly 1.5v then the pot as a voltage divider would do it.

[hispls]

I think the problem is that a diode doesn't act like a resistor (probably when it's first powered on) potentially giving you trouble.

Can you simply series 3 or 4 of the LEDs so that you drop 1.4-1.6V at each? Also typical flashlight batteries are 1.5V so perhaps something designed to work around a rechargeable AA battery (or replace it's voltage from another source) would help you get there?

I'd begin searching at projects that can be done around that type of battery. IDK if they still even make disposable cameras but those used to be a cheap source of parts for some projects.

It's been a long time out of school for me but IIRC a transformer needs to use AC so if you want to step up or down you need to turn your input into AC, run it through a transformer, then rectify back to DC. Might begin getting more complex than just cannibalizing something that exists for another purpose.

[Jessica]

https://store.schoolspecialty.com/OA_HTML/ibeCCtpItmDspRte.jsp?minisite=10206&item=1679539&gclid=CjwKEAjwydK_BRDK34GenvLB61YSJACZ8da3TIHRdAGssbADgv9BvhoXbQdMwGdhregyHovAaAthARoCaYnw_wcB

[DLHgn]

You should be able to put a high value resistor in series with it. Like a 10k ohm. A pot would work if set up as a voltage divider but is not necessary to light the led.

If you wanted exactly 1.5v then the pot as a voltage divider would do it.

I don't need exactly 1.5v. Can be between 1.45-1.65v. I looked at using a voltage divider. What kind of pot would I need?

[DLHgn]

I think the problem is that a diode doesn't act like a resistor (probably when it's first powered on) potentially giving you trouble.

Can you simply series 3 or 4 of the LEDs so that you drop 1.4-1.6V at each? Also typical flashlight batteries are 1.5V so perhaps something designed to work around a rechargeable AA battery (or replace it's voltage from another source) would help you get there?

I'd begin searching at projects that can be done around that type of battery. IDK if they still even make disposable cameras but those used to be a cheap source of parts for some projects.

It's been a long time out of school for me but IIRC a transformer needs to use AC so if you want to step up or down you need to turn your input into AC, run it through a transformer, then rectify back to DC. Might begin getting more complex than just cannibalizing something that exists for another purpose.

I can't use more than one LED and I really want to stay away from using an external power source such as a battery. I really need to be able to tap straight from the USB.

[DLHgn]

https://store.schoolspecialty.com/OA_HTML/ibeCCtpItmDspRte.jsp?minisite=10206&item=1679539&gclid=CjwKEAjwydK_BRDK34GenvLB61YSJACZ8da3TIHRdAGssbADgv9BvhoXbQdMwGdhregyHovAaAthARoCaYnw_wcB

What would this be for?

[Jessica]

https://store.schoolspecialty.com/OA_HTML/ibeCCtpItmDspRte.jsp?minisite=10206&item=1679539&gclid=CjwKEAjwydK_BRDK34GenvLB61YSJACZ8da3TIHRdAGssbADgv9BvhoXbQdMwGdhregyHovAaAthARoCaYnw_wcB

What would this be for?

1.5v

[DLHgn]

It's a Ac to Dc converter that outputs down to 3v. I need 1.5v.

[Jessica]

look closer it goes to 1.5v, the description is wrong, regardless these things are super common and can be picked up cheap and can go down to 1.5v. they also have severaltypes of adapter or you can just cut the wire. They even have a polarity switch.

So it should be a solution.

[Jessica]

here is another one

https://www.amazon.com/Seven-Star-Regulated-Universal-Converter/dp/B005IDTH76/ref=sr_1_2?ie=UTF8&qid=1475682580&sr=8-2&keywords=universal+power+supply+1.5v