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Topic: Powering Attiny (Read 1 time) previous topic - next topic

hanyc93

Jan 22, 2014, 07:46 am Last Edit: Jan 22, 2014, 07:58 am by hanyc93 Reason: 1
Referring to the attached picture, I faced a problem of powering Attiny.

I think it's caused by noise?
Do you have any suggestion to solve this?

Thank you.

Shpaget

No cap at the output of the voltage regulator?

hanyc93

Done shrinking the pic

Coding Badly


JoeN

#4
Jan 22, 2014, 10:37 am Last Edit: Jan 22, 2014, 10:55 am by JoeN Reason: 1
If you have access to an oscilloscope, take a look at the voltage coming off the regulator to see if it is steady and is at the voltage you are expecting.

You say that you have 5V coming off your regulator, right?  How do you know this?  Measurement with a multimeter, oscilloscope, or just faith that the regulator is doing what you think it is doing?  What kind of regulator is it anyway?  7805?
I have only come here seeking knowledge. Things they would not teach me of in college.

Erni

You say it keeps restarting, which propably meens that it is resetting.

Put a 10 KOhm resistor from reset to 5V, and a 0.1 uF capacitor from 5V to ground as close to the tiny as possible.

hanyc93


If you have access to an oscilloscope, take a look at the voltage coming off the regulator to see if it is steady and is at the voltage you are expecting.

You say that you have 5V coming off your regulator, right?  How do you know this?  Measurement with a multimeter, oscilloscope, or just faith that the regulator is doing what you think it is doing?  What kind of regulator is it anyway?  7805?


I don't have an oscilloscope at the moment.

The ouput of VR 7805 is about 5V measured using a DMM

hanyc93

#7
Jan 23, 2014, 04:51 am Last Edit: Jan 23, 2014, 07:06 am by hanyc93 Reason: 1

You say it keeps restarting, which propably meens that it is resetting.

Put a 10 KOhm resistor from reset to 5V, and a 0.1 uF capacitor from 5V to ground as close to the tiny as possible.


Doesn't this method reset attiny? I don't want it to keep resetting.

I don't have a 0.1uF C, may I use a 100uF instead? Does the value of C matters?

Thanks.

wes000000

From attiny datasheet, so pulling the pin high will not reset it.

Quote

1.1.4 RESET
Reset input. A low level on this pin for longer than the minimum pulse length will generate a reset, even if the clock
is not running and provided the reset pin has not been disabled. The minimum pulse length is given in Table 21-4
on page 165. Shorter pulses are not guaranteed to generate a reset.
The reset pin can also be used as a (weak) I/O pin.
"I have not failed. I've just found 10,000 ways that won't work." - Thomas A. Edison

hanyc93

Thank you very much! I will try this!

JoeN


Thank you very much! I will try this!


The capacitor that the other poster mentioned is used to smooth out any noise on the line.  A smaller cap reacts faster to AC.  100uF is actually pretty big.   You can find .1uF, 1uF, 10uF caps anywhere.  Got any old electronic junk?  You probably have a bunch of these and don't know it.
I have only come here seeking knowledge. Things they would not teach me of in college.

hanyc93

Thanks!!! Great help

hanyc93

Sad, 5V + 10k ohm to attiny reset pin doesn't solve the problem :(

Chagrin

Your AC/DC adapter is 6V and you're using an LM7805 to drop it to 5V. That's only a 1V difference, and the LM7805 is spec'd at a minimum 2V dropout voltage (the input must be 7V, minimum). I understand you're seeing 5V out so it seems to be working, but my assumption would be that it would become unstable as soon as you start pulling real current through it (dropout voltage typically rises with current).

The input and output capacitors on the regulator shouldn't be neglected either. .33uF between Vin and GND and .1uF between Vout and GND. The output can be unstable without them and you won't be able to see that with a DMM; need an oscilloscope for that.

Shpaget


Your AC/DC adapter is 6V and you're using an LM7805 to drop it to 5V. That's only a 1V difference, and the LM7805 is spec'd at a minimum 2V dropout voltage (the input must be 7V, minimum).


The picture says that with the 6V supply it works, but not with the 9V.

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