ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
dsk 13
Admin 8
Recent Posts
Grid problem??
by annemarie1. 08/21/17 01:10 PM
Bathroom electrical
by doc. 08/19/17 06:53 AM
electircal ageing test on IPC
by SIAME. 08/15/17 02:43 AM
electrical aging test on IPC
by gfretwell. 08/15/17 12:27 AM
"Line level" audio on Cat 5?
by gfretwell. 08/08/17 10:39 PM
New in the Gallery:
Gallery Test
Popular Topics(Views)
240,051 Are you busy
175,671 Re: Forum
167,890 Need opinion
Who's Online Now
0 registered members (), 69 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#177445 - 05/02/08 11:40 PM Capacitive Proximity Switch  
BigJohn  Offline
Member
Joined: Mar 2004
Posts: 391
Boston, MA
I need a hidden deactivation switch for a security system. I'm thinking of using a capacitive proximity sensor hidden behind a thin, non-metallic object that will activate a relay when a hand is passed over the object.

I've never worked with prox. switches before. It appears that most of these switches use a transistor for switching. Are these traditionally digital or analog outputs? Will putting a barrier in front of the switch cause it to constantly conduct some amount of current to the output (maybe in relationship to the distance of the object from the sensor)? Or do most of these have a threshold value for "on" or "off"?

Any help would be much appreciated.

-John


Tools for Electricians:

#177463 - 05/03/08 10:52 AM Re: Capacitive Proximity Switch [Re: BigJohn]  
twh  Offline
Member
Joined: Mar 2004
Posts: 916
Regina, Sask.
The ones I'm most familiar with are a two-wire switch. Typically, they would provide an input to a PLC, but I've used them to switch a small relay.

Put a barrier in front of it and it will change states very quickly. The distance is adjustable. Metal is quite easy to calibrate, grain is harder to calibrate and needs to be in direct contact, and a hand - I've never had a bin full of hands, but I'm quite sure that I've tripped them with my hand.


#177513 - 05/05/08 08:55 AM Re: Capacitive Proximity Switch [Re: BigJohn]  
LarryC  Offline
Member
Joined: Jul 2004
Posts: 783
Winchester, NH, US
Most prox switches I have worked with have a sensitivity adjustment. Metal sensing prox switches would work if the user wears a ring or holds keys or a tool up to the surface.

Larry C



Member Spotlight
Theelectrikid
Theelectrikid
Levittown, PA
Posts: 810
Joined: April 2004
Show All Member Profiles 
Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.010s Queries: 15 (0.002s) Memory: 0.7518 MB (Peak: 0.8759 MB) Zlib enabled. Server Time: 2017-08-22 01:55:10 UTC