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# Complete beginner

#### RyeRye

##### New Member
I am trying to make a simple circuit. Well it seems simple but it's really racking my brain there's so much information I don't know where to start

So the circuit I'm trying to make is for a 3v mini DC motor. The idea is when I turn the switch on the battery pack (x2aa batteries) the motor will turn on but also have an led that lights up to show it's powered on. The issue I'm having is when I set this up the led keeps flickering and is very dim.

If anybody could shed some light on this I would very much appreciate it.

The likely problem is that the battery voltage is falling too low for the LED.

A red LED with a 47 Ohm resistor may work; red LEDs have the lowest voltage drop, about 1.8V or so.
Other colours need higher voltages to conduct.

You must always have a series resistor with a normal LED to limit the current. 47 Ohms would set the LED current to around 20 - 25mA or so with new cells, down to a fraction of that when they are near flat.

The two AA cells will give around 3V with no load or low loads, when they are new. That voltage will drop steadily as they discharge, down to about 2V. It will also be pulled lower if the load current is high for the type of cell; a good brand alkaline cell can give much higher current than an economy type generic cell.

Maybe your AA cells are cheap and very poor quality .
Use new Name Brand Alkaline battery cells.

Again with ridicule. Try not to use named counties in you racism! MOD edit.

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LEDs operate over a 10% voltage range for brightness. So you cannot expect linear function to a motor unless you use PWM and ensure Vbat is always constant. Your battery has enough resistance to prevent this.

Sounds like they (motor and LED) are wired in Series. Try connecting them one at a time and report what happens.
Note, the LED will need a series resistor.
Note2, We're assuming a small DC motor such as

Mike.

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If you're using a white LED (2.7 to 3.3v typical), the 3v is barely enough to light it up.
If you're using a red LED (2v), you'll need a low value resistor to make sure it doesn't blow. If you want to risk the red LED blowing, you can HOPE the internal resistance of the battery is enough to prevent the LED from blowing. A secondary measure could be to make sure the motor is always running when the red LED is connected. That is, never connect the red LED to the batteries without the motor connected at the same time. This is, in general, a bad idea because the red LED will likely pop either way.
Use a 100ohm reisistor in series with the LED and wire the motor in parallel with the reisistor-LED.

Simple fix is more power, forget batteries get wall plug in DC adapter 3VDC@500mA run wires in safe place. Fixed supply current will extend motor life and control motor speed. If you must use batteries go with a lithium type battery that is rechargeable when light flickers or dims recharge. This time should be greatly increased with lithium battery only. Purchase new battery and charger use correct charger together only.
Last never give in never surrender, never forget, Ohms Law double the current any type battery simply parallel two three more batteries , you get more power, you must have more power or current in E= I *R.

Simple fix is more power, forget batteries get wall plug in DC adapter 3VDC@500mA run wires in safe place. Fixed supply current will extend motor life and control motor speed. If you must use batteries go with a lithium type battery that is rechargeable when light flickers or dims recharge. This time should be greatly increased with lithium battery only. Purchase new battery and charger use correct charger together only.
Last never give in never surrender, never forget, Ohms Law double the current any type battery simply parallel two three more batteries , you get more power, you must have more power or current in E= I *R.
Could you please explain what the OP RyeRye is planning - you seem so knowledgeable about what he would do.

This might simulate your circuit and show the battery resistance is too high for the motor with a no-load resistance of 8 Ohms. and thus the voltage may drop too much for AA batteries.

You can see I simulated the AA batteries with a realistic large C and ESR with a reset precharge of 1.54V.

The critical unknown is the DCR of the motor and the ESR of the battery must be < x% if you expect the voltage to remain with x% when started and realize, that most batteries are almost dead when Vbat is < 80% new. For LEDs, this means you need to use Red or Yellow 2.1V with a current limiting resistor.