Research on the DSC 1832 Series Alarm System

3/11 – Updated the smoke detector wiring per HSC tech support.

The DIY alarm system is not a new idea, and there are plenty of wireless “ready to go” systems where you just plunk the old thing down and it’s ready to go.

But that’s no fun. Meet the DSC 1832 PowerSeries alarm panel:

A simple kit for the 1832 from the homesecuritystore.com website
A simple kit for the 1832 from the homesecuritystore.com website

The system itself is pretty much plug and play — you connect power, a battery, and a keypad (over the proprietary but ripe for hacking keybus) and you’re ready to go.

Now you may at first think that you would connect the sensors in a simple configuration where the sensor shorts or opens the circuit to indicate fault. There is a simple reason why we don’t use that: what happens if somebody (or a squirrel) snips the wire? There are multiple configurations that this particular panel supports, the most interesting being the double EOLR (end of line resistor):

The DSC specified double EOLR configuration.
The DSC specified double EOLR configuration.

Simple but effective. Now, from the alarm panel’s perspective (assuming we use the recommended 5.6k resistors) and using a little bit of ES3 basic circuits:

  • 0Ω Fault – indicates a line fault (short) at some point before the detector and line resistor.
  • 5600Ω Secure – indicates the alarm contact is closed (using normally closed contacts)
  • 11200Ω Violated – indicates the alarm contact is open
  • Open circuit Tamper – indicates somebody’s scissors have handily snipped the wire

Cool right? So to wire up any zone in this fashion (motion detectors and door close-y inductive sensors are typical) you simply run your 4 wire strand from the panel to the sensor (remembering, of course, that your motion detector will require power wires too). And yes, if you were lazy you could use single EOLR at the panel and then have no idea of the line condition. But when we have resistors and electrical engineers, why not have a little fun? Most installers (looking at my lovely ADT system) usually don’t bother to put the resistor at the END of the line and instead wire it at the terminals on the panel. So if you do it yourself and do it properly, you’ll be paying less and getting a system that’s easier to troubleshoot down the line.

Smoke Detectors

Now comes the one that is slightly harder to decode. The system supports two and four wire smoke detector systems. I will briefly explain how exactly you wire those because it is exceedingly unclear without burrowing through multiple instruction manuals and reference guides.

The four wire smoke detectors should be thought of as a powered sensor, with a few exceptions. First, the system is designed to be daisy chained such that you could theoretically use every detector on one zone. In addition, the detector is what is called a “latching” device such that once it sees smoke (or heat) it will latch on until it is reset. The reset signal is initiated using a keypad sequence which causes the alarm panel to drop one of the PGM outputs low, disabling power to the circuit.  This loss of power resets any latched detectors. The justification behind the latching (besides FIRE) is so that if a detector goes off, it will stay latched and thusly indicating to you that it went off, until it is reset.

At the end, you use a relay in addition to a SINGLE EOLR across the terminals (double EOLR requires normally closed connectors to produce the resistances appropriately, as should be obvious when comparing the circuitry to the resistance table). Why? Because the alarm panel would have no way of knowing if power failed somehow to the detector circuits. When power fails with a relay across the signal lines, it will go open circuit and indicate trouble on the smoke detector zone line. Good, see?

Lastly, you also have the option (?) of installing a polarity reverser. When the alarm condition is triggered (usually attached to the siren output), this device will reverse the polarity of the smoke detectors causing all to sound. Pretty nifty, because the smoke detectors will function as sirens throughout the whole house even if no smoke occurred.

You can hook up the power to the PGM2 for the smoke detectors which allows the panel’s built in sensor reset function to reset the latched detector. Now, the problem is that the panel only provides 300mA of power from the PGM2 output. That limits you to three 4-wire detectors in the loop with every detector in “Alarm” state (according to the documentation for the polarity reverser). You may consider getting a relay to add current capacity because that is truly pitiful. The internal “AUX+” power rails need to be limited to 700 mA if you’re getting a UL inspection, but support up to 2.5 amps natively. Since we figure the detectors won’t be in the ALARM condition very often, you should be well within that limit. Here’s a wiring diagram I got from Home Security Store tech support with one of their relays to increase capacity:

Relay wiring to increase smoke detector capacity.
Relay wiring to increase smoke detector capacity.

Keypads

The keybus is a simple design with power, CLK, and single line bidirectional data. Just hook ’em all up in parallel (but not too exceptionally far apart) and they will all just work magically. I believe you have to tell the keypad which number keypad it is during setup…I’ll get to that during programming/once I’ve programmed this.

Why not wireless?

So the entirety of modern society has this fetish with “wireless” equipment, as if it offers inherent advantages over wired equipment. I will admit, copper lines do not have unlimited life (but neither do computers) and at some point you may experience line trouble especially if a small nefarious animal chews through your cables. Here, however, are the advantages (in my eyes) of wired systems:

  • RF has a lot of moving parts. Specifically:
  • The hardware needed is more expensive.
  • The line is not “guaranteed” RF interference can cause connection problems. Most protocols or spread spectrum communications can get around this, but also use more power.
  • You still have to wire the sensor! Well, not really…you could just use batteries. But who on earth wants batteries everywhere? In the conventional system you have one battery that backs up the whole system and has to be replaced every five to seven years. On the other system you have N batteries replaced at Y interval. Who wants to be replacing batteries all the time?
  • If you decide to upgrade your alarm system in 20 years you can STILL USE THE SAME WIRES while a lot of wireless equipment is proprietary. That means that if a wireless smoke detector dies for a discontinued system, you’re SOL but if a wired detector dies you can still get new ones because the “open the wire loop if problem” manner of communication is universal in the industry.

In short: wireless works well if running wires is expensive. If you still haven’t put the walls on your house or your system will be confined to a small space, wiring is cheaper and more reliable.

Programming

Each zone will have to be enabled, named, and set to the appropriate type of zone. In addition, you will have to add additional zone panels if your capacity exceeds the number of onboard zones (here I’ve budgeted to require exactly 8 zones).

You’ll have to setup the telephone numbers for your call system. The phone line is wired via a quick disconnect which routes the phone line through the system, allowing it to seize control of the line in the event of a communication need. Leaving the phone off the hook will not interfere with the operation of the alarm system should it be wired properly in this way.

Fire Zones

Be aware that fire zones are 24 hour zones. A signal on a fire zone  will, by default, summon the fire brigade. This is good, because if there is a legitimate fire, you will have people come save you (or your house if you happen to not be home). This is bad, however, because the fire brigade may be summoned for burned popcorn/bacon. There are several methods that the panel has for mitigating these problems which I will detail for you here:

  • Auto verified fire – Upon receiving a fire zone trip, the panel will reset all the detectors and wait for them to settle. It then checks all zones again. If a fire zone trips a second time, the fire brigade will be summoned.
  • Delayed fire – Upon the fire zone trip, the panel will raise all hell with bells and sirens and things. If you press any button on the panel (not the FIRE button), it will acknowledge the condition and stop the bells and sirens. If a second fire zone trips, it will summon the fire brigade.

Obviously choose wisely, and make sure people in your house know what to do if they burn the bacon. The fire zones are 24 hour active and there is no way to bypass them.

Components

The following are sourced from homesecuritystore.com, of which I have no affiliation. But they definitely have DIY alarm systems and a good array of literature.

Adjust the quantities above as you like. You can also poke around and see what else is available. Just so you know, this kit will allow only a true land line based connection. You can add cellular or other connections, but personally the personal IP connection which can email you and your friends seems good enough.

You’ll need to get your own alarm monitoring service to run over the land line, which will be pretty cheap and can get you a fairly good discount on homeowner’s insurance if you have the Fire.

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