Balanced inputs

[champson]

I decided to look at using balanced input mode, mostly as a way to reduce wiring and make the tamper detection a bit more secure.
I didn't have much luck testing with my PIR, so instead I made a circuit on a small piece of breadboard.
Basically, just the circtuit shown in the 'Gateway Setup' pages.

I found that the circuit has the following resistance values, and the voltages measured at the zone input:

No alarm conition:  1K1 ohms   1.34v
PIR alarm condition: 2K2 ohms  2.45v
Tamper condition:   O/C   5.46 v

However, the Gateway web GUI shows that the system is only detecting the normal and tamper states, not the PIR alarm state.  I have the zone properly configured in balanced mode.
Not sure what I'm doing wrong at this point :)

[vysocan]

Hello,

try new build, I've lowered the PIR threshold.

[champson]

Great, thanks Adam that worked perfectly.

[champson]

Hi Adam,  I ordered some more vibration sensors that I have been using, but unfortunately the manufacturer has changed the design.  Now, rather than being able to use external resistors (as you supplied with my gateway),  they have integrated the resistors into the unit.  It is possible to choose from a number of different values, the closest was 1K.   This resulted in values of 1K for no alarm and 2K for the alarm condition.  
This got me thinking.  I wonder if it would be possible to add a setting where one could fine tune the thresholds?

[vysocan]

Hello Charles.

there is rather generous threshold, since the voltage depends in 12V input which may vary from 14 to 10V. I would give it a try. 2k2 vs 2k, and 1k1 v 1k.

In conf.h are system wide macros:

#define ALARM_PIR        2600   // (3380 = 15.2V), (2700 = 12.6V)
#define ALARM_PIR_LOW    2100
#define ALARM_PIR_HI     3200
#define ALARM_OK         1500   // (1850 = 15.2V), (1500 = 12.6V)
#define ALARM_OK_LOW     1100
#define ALARM_OK_HI      1900
#define ALARM_TAMPER     0
#define ALARM_UNBALANCED 500

Wrong setting will cause unexpected tamper, or PIR events.

[champson]

Thanks Adam,  I will take a look at the code.  I did test it but found it a little unstable, so it must have been on one of the thresholds.
Good to know they are easily changed :)