Editor's Note:

In our January 2010 issue we run a grow-related security piece entitled "Staying Safe Inside" (pg. 64). As part of our indoor grow-themed special we wanted to include an article that served the interests of every stealthy grower. Unfortunately, we could fit all the info into four small pages, so we decided to run the more technical (and boring) details here in an online supplement. The appendix includes a parts list (from the story) as well as step-by-step instructions on assembling the door locking device discussed in the article... plus a few installation tips! Wow. - Nico.


Additional Note: Crimestopper’s instruction manual for the CS-2000 III can be found hereThis manual will aid you greatly when assembling the elecrical components of the mechansim.



The Invisbile Door Lock: How-To Intro

One relatively simple way to create an invisible door lock is to use a cheap off-the-shelf car-alarm system. To avoid questions by perceptive landlords and building managers, it’s important that there be no visible changes to the doorknob or door, which might suggest that you have security installed. This is why most off-the-shelf electric door-lock products can cause more problems than they solve, since they alter the outward appearance of the door more often than not.

A simple solution is to create homemade locks that basically involve pushing one or more deadbolts with parts that would otherwise be used to control an automobile’s electronic door locks. The adaptation of a car alarm to a door lock for a room is surprisingly simple and even slightly superior to the off-the-shelf solutions in price (around $100). Just as cars come with either two or four doors, it is possible to deadbolt either the doorknob side at the top and bottom, or all four corners of a single door, creating a last line of defense that would require property damage in order to penetrate. In other words, anybody who thinks they have a right to be in your growroom will have to saw their way to it!

A Bigger Picture 


Although the pictures and terminology may seem intimidating, the design is relatively straightforward. The idea is to control a car-alarm actuator with a power door-lock relay. The actuator converts circular motion from a motor into linear motion; a lock relay amplifies the car-alarm signals so that they can drive the actuator’s motor.



In this design, each actuator pushes or pulls a sturdy deadbolt on the inside of the door. The relay is driven by the car-alarm output, which you control from outside the door with a remote. (All of the circuitry, actuators and deadbolts can attract a lot of attention, so this system is not intended for the apartment’s front door.) A 1-amp, 12-volt “wall wart” power supply is sufficient to power the actuators and can be cut off of any unused electronic device you may have laying around. To ensure access to your room when the power goes out (a situation that would certainly demand access to a growroom), you can install the door-lock system with a battery backup. In the event of a power failure, a typical low-cost UPS-power backup battery (intended for a low-power computer and found in any electronic store) will keep the room accessible.


Should it become necessary, the system can be uninstalled with a drill in just a few minutes, leaving only screw holes behind. Reinstallation is just as quick. This system design has been demonstrated to work so long as nothing ever interferes with the movement of the actuator, and so long as one remote is paired with just a single car alarm (pairing one remote with multiple doors can lead to unpredictable results). Although you won’t be using the siren that comes with your alarm, you’ll still need it in order to program the alarm.


Parts List

• Door lock actuators: Crimestopper CS-610SI Power Door-Lock Actuator: $5 each

• Power door lock modules: Crimestopper CS-6600DLM Power Door-Lock Module: $4 each

It’s important to realize that the car alarm will not be able to drive the actuator by itself. The signal it sends out isn’t strong enough, so we must amplify the signal with a power door lock module. This is basically a pair of relays in one component which typically allow us to drive two actuators with one input signal. Most newer cars will already have power door lock relays, so this is an important separate component that probably won’t come included in the basic alarm package.

• Deadbolt(s): Stanley 6-inch Heavy-Duty Zinc-Plated Barrel Bolt: $6 each

The actuator arm is made of plastic, so the actuator should drive a deadbolt, which resists the motion of the door much more effectively because it’s made of better parts, but also because you have the option of firmly securing it into the wall and door.

• Radio receiver with two remotes, shock sensor, siren and indicator led: Crimestopper CS-2000III Series III On-Guard System with Remote Keyless Entry: $40

This is the locking mechanism’s brain. Even the most basic car alarms today have far more features than you will need. In fact, you’ll find that the most basic Crimestopper alarm has 2 extra remote outputs that you can use to control other items in your room. For instance, you could use one of the buttons on your keychain to turn a video recorder on and off – on when you’re not around and off when you are around.

• 12V 1 Amp - AC/DC Transformer: Available from electronics surplus stores for around $10, or for free if salvaged from old, unused electronics gear.

• Low-wattage UPS power strip: Tripplite Internet Office 350 VA 120V UPS: $35

Installation Tips

• Keep your battery backup upright; do not attach it to the door. Fix it into place somewhere it will not get splashed with water. You can do that with plumber’s hanger strap.

• Pay special attention to the connection between the actuator and the deadbolt, as well as their relative locations. You will need to bend a screw hook with vice-grips and a hammer to make this happen. With a little experimentation and patience, you will find a combination of connection and location which does not get stuck. It’s important to get this right because your only recourse if the deadbolt gets stuck is to drill a 4-inch hole through the door near each deadbolt.

• You may find that you have to insert pieces of plywood or scrap wood to get the deadbolt to align with its catch when the door is shut. If necessary, use one of the small plastic ties that comes with your alarm to improve the actuator-deadbolt connection.

• It will take numerous tests before you feel comfortable with the movement of your deadbolt into its catch.

• Place the deadbolt relative to the actuator such that the deadbolt’s movement does not involve a hard strike between two pieces of metal to minimize noise.

• Do not use a drill to fix the actuator to the door, as you might destroy the plastic.

• Keep a backup remote control somewhere in the house just in case yours becomes lost or broken.

Assembling the Electricals

Towards the end of the Crimestopper documentation (on page 15) is a schematic that shows a picture of how all of the alarm components fit together. You’ll find this to be really useful in figuring out how to make your connections.

There are four main groups of wire (“harnesses”) that you’ll have to plug into the alarm brain: the main harness, the override/program button harness, the LED harness and the power door lock relay harness (which you may have to order separately). You’ll have to establish connections to ground and +12v for both the alarm’s brain and the power door lock relay. And you’re going to want to, at least temporarily, hook up your system’s siren. The override/program button and the siren are essential for programming your alarm, which you’re going to want to do because the factory defaults don’t exactly serve the purpose we have in mind.

By far, the best way to connect these wires is to solder them together. Connect the ground and +12v connections first. When it comes to understanding how to connect up your actuators and power door lock modules, you should consult the lower-right-hand diagram of the “Power Door Lock Wiring” page in your Crimestopper documentation (page 6). You’ll notice in that picture that they show two connections to ground, but they don’t tell you what color the wires are. Well, maybe it’s obvious to them, but those wires are brown and white. If you leave one of them disconnected, the actuator won’t work in one direction. The +12v connection is far easier to identify because it’s the only wire dangling from power door lock modules that has a fuse attached to it.

The brain’s +12v connection can be found in the same way – it has a fuse attached to it (and it’s red). The chassis ground is the black wire third from the left on the main harness.

You’ll also want to strip the end of the yellow wire so that you can use it for programming. This wire tells the brain that the key is in the ignition.

You’re going to need to connect that siren up so that you can perform programming. This will involve connecting the siren’s red wire with the brain’s brown wire and giving it a pathway to ground. You can disconnect it later if you want. But for setup, it’s a critical component to help you get your bearings because it confirms the programming steps as you move through them. You will want to wrap the siren in some sort of blanket before you plug the entire system in. Now you understand why these alarms are so common – they only cost $40!

Solder green wires to green wires, and blue wires to blue wires. Cover all exposed wires with electrical tape. There are three default features that come standard with your alarm that interfere with what we’re trying to do:

• Passive Arming
• Ignition Controlled Locks
• Active Re-Arm

Follow the instructions for “Option Programming”. When the system flashes the headlights, you’ll hear the relay inside of the brain clicking. It’s not necessary to hook headlights up in order to deactivate these features. Disconnect the siren and you’re done.