Normally closed solid state relay (DC output)

Forum 2005-2010 (read only) Hardware Interfacing
1

I need a SSR that is normally closed (if my Arduino dies the line should remain closed)

I googled and found this one: LPBD100, but boy is it expensive.. $100+

I assume this is because this is military grade avionics equipment..

FEATURES/BENEFITS
? Dual output: two relays in one package
? Normally closed output

250mA, 100Vdc Normally Closed

Any cheaper alternatives?

2

look at car shops :wink:
something like this? http://cgi.ebay.com/DIP-RELAY-SPST-NORMALLY-CLOSED-CLARE-PRMA1B05B-5V-COIL-/250733161120

3

good idea.. is this solid state?
I will be switching this on and off a lot and I don't want mechanics involved..

4

my dad uses those...
and sorry i have no idea if that one is ssr...
BUUUUUUT
Long life > 1 billion operations

5

Why not use a p-chanel MOSFET? Take a look at this link: Microcontroller Interfacing

You can replace the MOSFET in the diagram with a much beefier one if desired.

6

thanks for the replies.

I like radexito's option best as it seems to be easiest to implement in my case.

7

Thanks for your comment.

I plan to use the relay to open a circuit and force the current to go thru a resistor in series.

------- NC relay -------
| |
--(Resistor)--

This is an alternative solution with my troublesome idea of emulating the thermistor value (see my post in HW/Interfacing)

It will happen only if i need to raise the temperature (add more resistance to the existing thermistor reading)

The relay will be controlled by Arduino Digital pin