relay or opto coupler
Archiver
Posts: 46,084
Hi guys,
im looking to setup a basic watering system using my BS2. To do this i need to
control a bunch of solinoids to turn the water flow on and off.
I had been going to just hook a relay up but after reading one of the other
threads i thought hmmm
maybe i could use an opto-coupler. they are alot cheaper then relays and also
isolate the input.
I have never used these before so i was wondering could a 4N28/4N25 or 6n138
device be used for this application in place of the relay.
if so would i need any other hardware?? resistors etc.
I hope someone could help
Thanks
Peter Rogers
[noparse][[/noparse]Non-text portions of this message have been removed]
im looking to setup a basic watering system using my BS2. To do this i need to
control a bunch of solinoids to turn the water flow on and off.
I had been going to just hook a relay up but after reading one of the other
threads i thought hmmm
maybe i could use an opto-coupler. they are alot cheaper then relays and also
isolate the input.
I have never used these before so i was wondering could a 4N28/4N25 or 6n138
device be used for this application in place of the relay.
if so would i need any other hardware?? resistors etc.
I hope someone could help
Thanks
Peter Rogers
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
current. However, if the valves are the 24 volt AC variety, you could use a
triac and one of those triac-driver optoisolators for each solenoid.
Original Message
> im looking to setup a basic watering system using my BS2. To do this i
need to control a bunch of solinoids to turn the water flow on and off.
>
> I had been going to just hook a relay up but after reading one of the
other threads i thought hmmm
> maybe i could use an opto-coupler. they are alot cheaper then relays and
also isolate the input.
> I have never used these before so i was wondering could a 4N28/4N25 or
6n138 device be used for this application in place of the relay.
>
> if so would i need any other hardware?? resistors etc.
Many SSR's are made with LED inputs that are optically coupled to a
solid-state output with various forms of input and output conditioning and
protection. In other words, they are often optocouplers with everything you
wish you could have thought of adding to them. If you are going to be
switching AC, there are many inexpensive choices, for example, a small Sharp
SSR that Radio Shack sells (or used to anyway) can handle a couple of amps
and switches by energizing the LED with low-current DC. You can accomplish
the same with a .49 optocoupler, a small Triac on a heat sink and half a
handful of ten-cent parts. If you are switching DC, you will need something
with a transistor or SCR output. There are a number of small SSR's available
that fit the bill and are, granted, a bit larger than the .300 dip
optocouplers that are commonly used. There are also large optocouplers in
various package types that you may want to consider, but these tend to
become more costly.
You may find it least expensive to use some common relays, but I'm always in
favor of protecting the controller's output pin optically in any case. The
ideal solution for you is more likely small DIP optocouplers between your
outputs and your relays whether electro-mechanical or optical.
BTW, don't forget to consider the EM spikes you'll deal with from your
solenoids...
Chris
>
Original Message
> From: Peter Rogers [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=s-hMDVhL9xVRzNuawLg9mDeNuNdDWa5WEk03x394ssFfp57_4vdIUDCCOycLh5ERGLASF8s83ULkjT_jcQ]molly7@o...[/url
> Sent: Wednesday, September 26, 2001 4:36 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] relay or opto coupler
>
>
> Hi guys,
>
> im looking to setup a basic watering system using my BS2. To
> do this i need to control a bunch of solinoids to turn the
> water flow on and off.
>
> I had been going to just hook a relay up but after reading
> one of the other threads i thought hmmm
> maybe i could use an opto-coupler. they are alot cheaper then
> relays and also isolate the input.
> I have never used these before so i was wondering could a
> 4N28/4N25 or 6n138 device be used for this application in
> place of the relay.
>
> if so would i need any other hardware?? resistors etc.
>
> I hope someone could help
>
>
> Thanks
>
> Peter Rogers
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
>
>
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