How to Create a Basic Wireless Door-Lock Release System
A wireless door-release system works the same way a garage door opener works. As shown in the illustration above, a radio frequency transmitter is used to signal a receiver. When the receiver receives the signal from the transmitter, it changes the state of a set of electrical contacts on board the receiver. These contacts are used to activate an appliance, such as a garage door opener, an electric strike or an electromagnetic lock.
In the basic electric strike system illustration above, a normally open switch is closed to allow power to flow to a fail-secure electric strike. A wireless door-release system substitutes a wireless receiver for the normally open switch in the illustration. One big difference is that, unlike a normally open switch, the wireless receiver requires power. Below is an illustration of the same electric strike system using a wireless receiver.
Notice in the illustration above that I have shown a power supply with separate outputs to power the receiver and the electric strike. I recommend this method to simplify wiring.
The biggest obstacle to having a completely wireless system is the electric locking device. At 12 volts DC, the receiver will probably draw less than 100mA during activation and less than half of that while on standby. It could certainly be powered by a couple of lantern batteries. Some electric strikes draw as little as 240mA at 12 volts DC, but even that will exhaust batteries quickly.
Wiring can be reduced by creating a battery operated wireless release system. To create a battery powered system, use a stand-alone electronic access control lock such as the Alarm Lock Trilogy that comes standard with remote release, or the Kaba-Ilco Eplex with optional remote release. These locks are battery operated independently of your wireless release system. See diagram below:
Wireless release system installations are more complicated these days because the system now must share the airwaves with a lot more stuff. Wireless routers, cellular and microwave towers, radio communications facilities and even computers can interfere with the wireless release system.
Notice on the illustrated wireless receivers in this article the bank of "dip switches." Dip switches are small rocker switches with two positions: on and off. Thinking of the dip switches in terms of computer logic, "on" would equal a one, while "off" would equal a zero. The ones and zeros you input via the dip switch bank communicate to the logic board the frequency at which to transmit or receive.
Many wireless receivers use dip switches to select the radio frequency that the system uses. Dip switch settings in the receiver and transmitter must match in order for the system to work. If your system is not working, make sure the frequency settings between the transmitter and receiver match. If they do, and the system still doesn't work, the problem may be radio interference. Select another frequency in both transmitter and receiver and try again. Repeat until the system works.
If this method does not work, the interference problem may be insurmountable and you may not be able to use a wireless system. In Rockefeller Center, in NYC, for example, the doppler radar system used to track local weather effectively prohibits the use of wireless products (including cell phones) above a certain floor. If there is a radar installation or microwave antenna farm near your wireless release system installation, that might be the reason it does not work.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2009 Tom rubenoff