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5 Threads found on edaboard.com: Alarm Open Circuit
I have a 12v power supply and a flow switch which is closed when water is flowing through it and open when water isnt. I want to make a simple piezo alarm + LED light that tells me (comes on) when water STOPS flowing. How do I do this? That is, how do I take a normally closed switch and make it normally open? Simple is best for me and the (...)
This is simplest laser alarm, and works very fine, I use it like multiple sensors for SMS alarm. Its very very simple uses opto transistor IRE5 5mm or LTR4206 3mm, or You can use any opto transistor. circuit can be used on daylight and on open. Laser torch is chiper chinese 1mW 5mW. Use second circuit from (...)
Hello, Why don't you try using a window comparator circuit. Fire alarm circuits work as a "short" for alarm and an "open" is circuit trouble. Using a LM339 Quad comparator would allow you to build 2 complete comparator circuits. If the micro you are using has (...)
I have the need for an alarm when house power fails. I purchased a sump alarm which trips on high water. The sump alarm probe is normally (low water) open. When water rises it closes and the alarm goes off. I want to substitute a normally open ciruit when house power is applied which (...)
what is your request, i fact it is not easy to realize the VSWR alarm accurately! so you should provide more information for your request If you have 7 dB attenuate (including filter and cable loss) between amplifier and antenna, is impossible to see if antenna end is open, shorted or connected correctly if approve