Multimeter and voltage dividing

Other Hardware General Electronics
1

Hello!

So I am pretty new to electronics and all that, so my question will probably be really stupid. Anyway, I want to connect 5 LEDs and a thermistor to attiny85. I managed to do that but I haven't got any other battery suitable for my project size other that a 9V. But I need 4 - 5.5 V for attiny85, so I need to lower the voltage. I was thinking of making the voltage divider so it gets me 4.5 v. I know I need two resistors of same value in series and 4.5V will be where they connect. But as a total noob with multimeter I don't know where to put my two thingies to check if the voltage is 4.5V. The red cable of multimeter goes to the divider output and the other to ground? I tried and it doesn't give my anything. With that I just want to make sure it works before I start putting LEDs. Also, everyone puts two 10k ohm resistors in series(even tho they say it doesn't matter as long as they have the same value). So can I put my two 1 ohm resistors in series? Will that change anything? I attached a picture so you can see how I connected everything before checking it with multimeter. I hope you can help me, sorry if this is a dumb post but I can't find how to connect multimeter to voltage divider circuit anywhere online :frowning: .

Best regards
Me.

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2

It unfortunately doesn't work quite that way. Just for example if I place two 10K resistors in series and apply 9 volts to one end and common ground to the other I will likely read about 4.5 volts between the junction and common. Looks good right till I place another circuit in parallel with one resistor in my divider. To complicate that further my load will not draw a constant current making things worse.

You have 9 volts and you want 5 volts. Look towards a cheap buck converter 9 V to 5 V or a 5 V regulator like an LM7805 or a good low dropout 5 V regulator. Less getting into details a simple divider is not a viable solution.

Ron

3

Oh dammit. Ah... I was really hoping it could work cause now because of the coronavirus I can't order anything :cry: . Well then , thanks for answering. Cheers :slight_smile:

4

Or use a mobile phone charger, lots of them around, 5V output.

5

Wow! Thanks alot, great idea! Man this makes things so much easier.