This door minder electronic project uses an IR beam to monitor door & passage-ways or any other area. When the IR beam is broken a relay is tripped which can be used to sound a bell or alarm. This door minder electronic project is suitable for detecting customers entering a shop, cars coming up a driveway, etc. Because the IR beam is very strong distances over 25 yards can be monitored with electronic circuit . This circuit must be powered from a 12volt DC supply .