[SOLVED] Generate +5v on boot

Other Hardware General Electronics
1

Hi,

I'm using a latching relay. It is important that the relay keeps open as long as the Arduino does not give HIGH on the correct pin. While this is ok, i have found out that if i turn off the unit while the pulse for closed relay is sent, the pulse to open it again is naturally interrupted. So when the unit is turned back on i have a relay latched in the closed position until the Arduino completes its boot time and pulses the open pin.

So, is there a way of with only electronics to generate a pulse for 2-3k ms to make sure the relay stay latched in open until the arduino boots and gets all its pins straight?

i have tried google, but with lack of a good electronics vocabulary, i only get pulse generators and 555 time modules. :slight_smile:

2

I solved it with a PNP transistor. :slight_smile:

3

Hello,

I think you're looking for the term PULL-UP, which will keep 5V, even when the Arduino has the reset button pressed.

4

fesanb:
I solved it with a PNP transistor. :slight_smile:

Ok, please add [Solved] at the beginning of the title

5

rtek1000:
Hello,

I think you're looking for the term PULL-UP, which will keep 5V, even when the Arduino has the reset button pressed.

A pull up cannot go low, therefore the relay is always open.

6

fesanb:
A pull up cannot go low

Will be?

When the Arduino activates the output low, the pull-up resistor will be disregarded.

7

fesanb:
i have tried google, but with lack of a good electronics vocabulary, i only get pulse generators and 555 time modules. :slight_smile:

A 555 monostable is what I was thinking of immediately. Trigger it with the Arduino (short pulse) - then let the 555 produce the long pulse for the relay.