SPST relay replacement

[signumx]

Hello everyone,

I want to replace some SPST electromecanic relays by something that would be less space and current consuming. I found digitally controlled analog switches and Solid State Relays - which are working fine - but these are rather expensive. I'd like to know if there is any other options that you people could think of.

What the relays are doing is simply open or close the loop for signal lines coming from a motor control module. This module is somehow a "black box". All I know is that square wave signals of 60Hz, 10Vpp are coming out and when a path is closed, a motors run. I tried to use enhancement mode Mosfets but since I don't have a common ground reference between my circuit and the module, it's not working (i.e. the Drain-Source is always conducting no matter if a voltage is applied to the gate or not).

Thank you.

 

[dbaird]

Depending oh what coil voltage and contact current rating you need Phoenix Contact offers 6.2mm wide relays that might work for you. Take a look at:

http://s48.yousendit.com/d.aspx?id=10VEWTK6OAQTT0B3689AS8EKT0

David Baird
mrbaird@hotmail.com
Sr Controls Designer
EET degree.
Journeyman Electrician.

 

[itsmoked]

Look at reed relays some can be very small.

 

[analogkid2digitalman]

Optoisolator?

Wheels within wheels / In a spiral array
A pattern so grand / And complex
Time after time / We lose sight of the way
Our causes can't see / Their effects.

 

[MMAshwin]

Hi,

Depending on the current requirments of you motor then what about an analog switch. See :-

http://dbserv.maxim-ic.com/tarticle/view_article.cfm?article_id=90

but remember these do have an on resistance (2 ohms & above) unlike your relay so if your motor draws lots of current then you may need to be prepared for smoke !!

Any help ?, yes no let me know.

Regards