4/20/17 – Other Circuits

Other Circuits:

ALARM SET
When an alarm comes in, turn on the corresponding Annunciator light and then sound an audio alarm that will stay on until you press one of the two ‘Alarm Reset’ buttons. You could do this with software – turn an I/O on and then monitor another line to see when the reset button is pressed or… push this to hardware.

I pulse one I/O line (low/high/low). This triggers an opto-coupled SCR. The SCR keeps the audio alarm on until power is interrupted (The two alarm reset buttons).

IMG_1099

ALARM RESET
Conversely, when an alarm clears, turn off the Annunciator light and turn on another alarm for about 0.5 seconds. Again, you could do this in software – raise an I/O, wait 0.5 seconds and then lower the line. Or… push this to hardware.

Pulse an I/O line – if this case, set the I/O line low and immediately raise it back to high. The pulse triggers a 555 timer set for 0.5 seconds. You get a brief tone alerting the operator an alarm has cleared.

IMG_1100

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s