In order to run the following motor at a reduced speed I want to drop the power running my ATTiny85 project from approximately 5 to approximately 3V (the ATtiny & other components will still run at 5V).
Looking in the internet I came across the following: How to convert D.C 5V to 3V - YouTube. Reaction in the comments was mixed.
Is this a good/safe thing to do in this case or should I consider another approve?
This looks like it might be a better option LM317 voltage regulator: Pinout, CALCULATOR, and circuits but I would like to hear other's opinions.
Both approaches are incorrect.
You control the speed of a motor using PWM. You’ll need a driver transistor if you’re driving the motor in one direction or an H bridge if you need reversing.
Some basics here: Overview | Arduino Lesson 13. DC Motors | Adafruit Learning System
The voltage regulator can work but if you are controlling the motor with the Arduino you'll need a transistor or MOSFET anyway and it's easy to add PWM. With PWM you can tweak the speed in software and you can use a full-voltage "kick", if necessary, to get the motor started.
A voltage regular divider won't work because the motor affects the resistance in one leg of voltage divider and that messes-up the voltage. You can use one resistor in series with the motor, so the motor is part of the voltage divider, but you'd have to find the right resistor value and you might not get enough startup current to get the motor started.
Thanks all, I didn't think of use the ATtiny to control the speed. I was going to run it straight off of the power but I do have one PWM pin free so will investigate that further.
@WattsThat, Last questions, referring to Overview | Arduino Lesson 13. DC Motors | Adafruit Learning System
I only 2N4401 which I see I can use instead of a PN2222 but with respect to diodes I have 1N5819; I can't work out is these would work and if so do I need to adjust the resistor for any of these changes?
The 2N4401 is ok but not optimal. It’s probably okay for testing so long as you don’t lock up the motor.
A mosfet would be best since the motor is 60ma no-load which means it can go as high as about 600ma when stalled - which the 2N4401 cannot manage. It will also be limited by the drive current available from an AVR pin which should be limitited to no more than 30ma. A proper mosfet can do this with no concerns, a bipolar transistor needs a careful selection to meet all the criteria.
The base resistor for the 2N4401 could be anything in the range of 150 to 270 ohms, the lower end of the range is better as it will provide more voltage to the motor when it is drawing higher currents.
The 1N5819 diode is fine in place of the 1N4001.
Thanks again, then using a Mosfet I will use RFP30N06LE as per http://bildr.org/2012/03/rfp30n06le-arduino/
@WattsThat just one more question. The link listed here uses 10 k ohms resistor, does that sound right?
