problem when the power first enabled to the MCU?

[wolfheart_2001]

hi,

i always add a reset button in my projects since usually my program dont run correct when the power first enabled unless i press it.

so does anyone know a simple circuit to do reset(provide high volt to reset pin) when the power first enabled and then provide 0 volt after short time?

 

[IanP]

There are many of these circuits on the market, but I would suggest to you the DS1232 from MAXIM/DALLAS (free samples available). It provides H and L active resets and allows you still to use external reset button.
INfo on this chip you can find here:
**broken link removed**

 

[SphinX]

hi,

so does anyone know a simple circuit to do reset, provide high volt to reset pin when the power first enabled and then provide 0 volt after short time?

You can use a cap in series with resistor to do that.
Connect the the cap to VCC and the resistor to GND

Then connect the reset pin to the node that connect the cap and resistor.

Use 8.2k for resistor, 10uF for the cap

This method used as reset circuit for 8051 uC

If you use AVR, you will reverse the cap and resistor only.

Bye

 

[h.mirhosseini]

Hi
Plz tell to me What you machine(8051,avr,pic,....)
but I think that your power supplay is not good and have large time constant.
you can use one cap one diode and one resistor:

| Vcc ..........| Vcc
/..................._|_
\ ..10k............/\ Diode
/.....................|
\____________|_________RST Pin (if activ Low)
_|_
___ 10uf
|
|
| GND

 

[irfansyah]

Hi
Plz tell to me What you machine(8051,avr,pic,....)
but I think that your power supplay is not good and have large time constant.
you can use one cap one diode and one resistor:

| Vcc ..........| Vcc
/..................._|_
\ ..10k............/\ Diode
/.....................|
\____________|_________RST Pin (if activ Low)
_|_
___ 10uf
|
|
| GND

I think mr. wolfheart wants the other way around, i mean the RST pin is active HIGH and normally LOW for normal operation. To do this, simply reverse it, Vcc becomes gnd, and gnd becomes vcc, except for the diode.
CMIIW

 

[HINDI]

HI all

u have to use a supervisory circuit , while the start up moment is very noisy.

https://www.techonline.com/community/member_company/non_member/tech_paper/336/content_33711

**broken link removed**
also , microchip application note [AN607,AN686] .

salam
hindi

 

[HINDI]

HI

U can use mcp120 or mcp130 from micrchip, or DS1232 .

Salam

Hindi

 

[eDance]

You should put a capacitor between VCC and RESET nodes, and a resistor between RESET and GND nodes. The cap & res' value can be various, depends on the reset timing which specified in the controller's datasheet.

 

[echo47]

Please, no more RC reset circuits in this world! They misfire too easily.
Instead, use an inexpensive power-up reset chip, like the ones mentioned above.

 

[ElecThai]

Give you use DS1833 for Reset Active high for 8051 MCU