Subject: Will this circuit work?
From:
[email protected] (smpaladin)
Date: 9/26/2004 8:44 AM Central Daylight Time
Message-id: <
[email protected]>
http://www.geocities.com/smpaladin/circuit1.gif
This is what the above circuit is supposed to accomplish: As long as
a magnet is held above the hall sensor, it will turn on the coil. It
does that by utilizing a power transistor.
Will this setup work properly? Will it work properly if up to ten of
these circuits are connected to eachother and how much battery power
would I need to run it?
Hi, Paladin. There are many types of Hall Effect sensors, and you're not too
specific about which one you're using, so I can't say for sure. However...
Many hall effect sensors are made with "open collector" output. That means
that, when they're on, their output pin will sink a few mA of current from a
pullup resistor or other source.
If you've got a type like that, you might want to try using a PNP transistor
and try something like this (view in fixed font or M$ Notepad):
.----------o--------------o----.
| | | |
| | | |
| | | |
| | .-. |
| .----o---. R| | |
| | + | | | |
| | | '-' |
| | Hall | ___ | |<
| | Effect o----|___|-o--|
--- | Sensor | R |\
- | | |
| | | .---o
| | - | | |
| '----o---' | |
| | | C|
| | - C|
| | ^ C|
| | | |
'----------o---------------o---'
created by Andy´s ASCII-Circuit v1.24.140803 Beta
www.tech-chat.de
Choose R such that about 1/10th of the current required by the relay coil will
be drawn by the base (note that many of these hall effect sensors are limited
to about -20 mA output current, so keep that in mind).
I hope this works for you. Be sure to check your sensor to check the specs.
If you're not sure, feel free to post again with more information. Battery
voltage, relay coil resistance, sensor type would all be helpful.
Good luck
Chris