simple 110v isolated relay circuit
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Posts: 46,084
I know this one has been discussed hundreds of times but...I am overloaded
with the different methods of switching on/off a 110v, 10amp load using
TTL. Some use just a simple relay others use many components and SSR's.
Isolation would be preferred. I am just looking for the lowest component
count, stable, elegant, and of course inexpensive method. I need to make
(4) switches and was thinking of using optoisolators and simple relays.
Thanks, Dan
with the different methods of switching on/off a 110v, 10amp load using
TTL. Some use just a simple relay others use many components and SSR's.
Isolation would be preferred. I am just looking for the lowest component
count, stable, elegant, and of course inexpensive method. I need to make
(4) switches and was thinking of using optoisolators and simple relays.
Thanks, Dan
Comments
no.D1210 would work 120vac@10A) and you can drive these with low current, 3
to 32vdc. This would give you total isolation from the ac and require few
parts. If I was doing it with a stamp, I would use a darlington transistor
to switch the relays to cut switching current requirements from the stamp.
These relays are inexpensive, however, there are safety requirements to
consider. You may cut the cost by going to a conventional mechanical relay
and using a transistor to switch it. Check out this web site for wiring
ideas.
Jim
http://www.geocities.com/jimforkin2003/
Original Message
From: daniel.d.dangremond@j... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=gjnYkisgnSarIMQZQhsa2DabAaYdeg9w4Us3PmDFYnZgCTYBNovrJCq7BZx9IvoVu70nxj4nlF1DlOeu6-40IMA]daniel.d.dangremond@j...[/url
Sent: Tuesday, May 20, 2003 11:52 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] simple 110v isolated relay circuit
I know this one has been discussed hundreds of times but...I am overloaded
with the different methods of switching on/off a 110v, 10amp load using
TTL. Some use just a simple relay others use many components and SSR's.
Isolation would be preferred. I am just looking for the lowest component
count, stable, elegant, and of course inexpensive method. I need to make
(4) switches and was thinking of using optoisolators and simple relays.
Thanks, Dan
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certainly isolated betweeen two circuits. No need to have
optoisolators if you are using a relay.
-Dustin
--- In basicstamps@yahoogroups.com, daniel.d.dangremond@j... wrote:
> I know this one has been discussed hundreds of times but...I am
overloaded
> with the different methods of switching on/off a 110v, 10amp load
using
> TTL. Some use just a simple relay others use many components and
SSR's.
> Isolation would be preferred. I am just looking for the lowest
component
> count, stable, elegant, and of course inexpensive method. I need
to make
> (4) switches and was thinking of using optoisolators and simple
relays.
> Thanks, Dan
> Use a relay. Very efficient and easy to use. Also, a relay is
> certainly isolated betweeen two circuits. No need to have
> optoisolators if you are using a relay.
>
> -Dustin
ditto.
use a ULN2003 to drive the relay(up to 7 actually). the Darlington
can handle the back emf when the relay opens as it has an internal
diode. the darlington will suffice as an isolator, but you really
don't need anything more than enough power to handle the relay coil.
As a note, you could use off board relays and let the darlingtons
swith them.
but, if you want the lowest part count as the goal, there are solid
state relays that will operate on 5V so all you need is the relay
direct to the stamp pin. is one part low enough?
Dave
Dave
>
> --- In basicstamps@yahoogroups.com, daniel.d.dangremond@j... wrote:
> > I know this one has been discussed hundreds of times but...I am
> overloaded
> > with the different methods of switching on/off a 110v, 10amp load
> using
> > TTL. Some use just a simple relay others use many components and
> SSR's.
> > Isolation would be preferred. I am just looking for the lowest
> component
> > count, stable, elegant, and of course inexpensive method. I need
> to make
> > (4) switches and was thinking of using optoisolators and simple
> relays.
> > Thanks, Dan
> I know this one has been discussed hundreds of times
> but...I am overloaded with the different methods of
> switching on/off a 110v, 10amp load using TTL.
> Some use just a simple relay others use many components
> and SSR's.
> Isolation would be preferred. I am just looking
> for the lowest component count, stable, elegant,
> and of course inexpensive method. I need to make
> (4) switches and was thinking of using optoisolators
> and simple relays.
> Thanks, Dan
Option 1: SSR
SSR bricks are definitely the simplest to interface,
and are optically isolated. One brick, four wires.
Bolt it to something to act as a heat sink panel,
and you're done... You can think of the equivalent
circuit as an LED of the optoisolator on one pair of
screws (which you drive from the Stamp like any OTHER
LED), and an SPST switch output on the other, which
goes in series with the hot lead of your AC load.
Lots of sources for these, and you can often find them
cheap by the handful at almost any good sized ham swap.
One "big" name in SSRs is Opto-22:
http://www.opto22.com/products/sys_level_hard.asp
Here's an image of a screw terminal SSR:
http://www.opto22.com/products/complvl_ssrs.asp
You can also get little racks and plug in SSRs from them.
You can also get Omron and other suppliers through about
any electronics house like Digikey or Jameco...
Option 2: Roll your own relay driver
To "roll your own", IMHO the simplest is use an opto
isolator with enough "oomph" on the output transistor
to directly drive a low voltage DC 10A relay. No extra
transistor required. You can get quad isolators from
Digikey, et al. to reduce package count.
Remember, you'll need a 1N4001-1N4004 "kickback diode"
wired "back biased" across each relay's coil to prevent
the relay from damaging the opto's output transistor
with spikes as it shuts off. There may be some
optos available with built-in kickback diodes, too,
but I personally prefer to use a separate diode to
make SURE it's done right, and is accessible for replacement.
The diode is best placed on the PCB to make sure the
polarity is right, but if using chassis mounted relays
you can always simply solder the diode right to the
coil terminals as well.
I'd advise adding a small fuse to the relay supply
to help protect your relay driver circuit.
BTW, if you're rolling your own relay interface,
you should definitely isolate the relay power from
the processor's to keep switching glitches from messing
with the processor. You don't need a second supply though.
If for instance you decide to use 12V relays and your
app only needs the Stamp's internal regulator, simply
use a 1N4001 blocking diode and a filter cap on the Stamp
side of the diode to create a "local" supply for the
Stamp from the relay's supply. The cap will "carry the
Stamp through" the glitch time. If you need more current,
use a LM7805 regulator circuit to derive a nice clean
+5V@1A from the relay's 12V supply. The app notes on the
7805 spec sheet shows the basic regulator circuit.
Good luck.
- Keith Mc.
--
"Diode: What happens to people that don't die young..."
as a note on the lowest parts count, the Darlingoton '03 have the
internal diode for this purpose. Uln2803 8 out or ULN2003 7 out.
BS2, one darlington, 4 relays, 6 parts. lowest price
BS2, 4 SSR's, 5 parts. lot of $$$
Dave
--- In basicstamps@yahoogroups.com, "Keith Mc." <acti@P...> wrote:
> In [noparse][[/noparse]basicstamps], daniel.d.dangremond@j... wrote:
> > I know this one has been discussed hundreds of times
> > but...I am overloaded with the different methods of
> > switching on/off a 110v, 10amp load using TTL.
> > Some use just a simple relay others use many components
> > and SSR's.
>
> > Isolation would be preferred. I am just looking
> > for the lowest component count, stable, elegant,
> > and of course inexpensive method. I need to make
> > (4) switches and was thinking of using optoisolators
> > and simple relays.
> > Thanks, Dan
>
> Option 1: SSR
>
> SSR bricks are definitely the simplest to interface,
> and are optically isolated. One brick, four wires.
> Bolt it to something to act as a heat sink panel,
> and you're done... You can think of the equivalent
> circuit as an LED of the optoisolator on one pair of
> screws (which you drive from the Stamp like any OTHER
> LED), and an SPST switch output on the other, which
> goes in series with the hot lead of your AC load.
>
> Lots of sources for these, and you can often find them
> cheap by the handful at almost any good sized ham swap.
> One "big" name in SSRs is Opto-22:
> http://www.opto22.com/products/sys_level_hard.asp
> Here's an image of a screw terminal SSR:
> http://www.opto22.com/products/complvl_ssrs.asp
> You can also get little racks and plug in SSRs from them.
> You can also get Omron and other suppliers through about
> any electronics house like Digikey or Jameco...
>
>
> Option 2: Roll your own relay driver
>
> To "roll your own", IMHO the simplest is use an opto
> isolator with enough "oomph" on the output transistor
> to directly drive a low voltage DC 10A relay. No extra
> transistor required. You can get quad isolators from
> Digikey, et al. to reduce package count.
> Remember, you'll need a 1N4001-1N4004 "kickback diode"
> wired "back biased" across each relay's coil to prevent
> the relay from damaging the opto's output transistor
> with spikes as it shuts off. There may be some
> optos available with built-in kickback diodes, too,
> but I personally prefer to use a separate diode to
> make SURE it's done right, and is accessible for replacement.
> The diode is best placed on the PCB to make sure the
> polarity is right, but if using chassis mounted relays
> you can always simply solder the diode right to the
> coil terminals as well.
>
> I'd advise adding a small fuse to the relay supply
> to help protect your relay driver circuit.
>
> BTW, if you're rolling your own relay interface,
> you should definitely isolate the relay power from
> the processor's to keep switching glitches from messing
> with the processor. You don't need a second supply though.
> If for instance you decide to use 12V relays and your
> app only needs the Stamp's internal regulator, simply
> use a 1N4001 blocking diode and a filter cap on the Stamp
> side of the diode to create a "local" supply for the
> Stamp from the relay's supply. The cap will "carry the
> Stamp through" the glitch time. If you need more current,
> use a LM7805 regulator circuit to derive a nice clean
> +5V@1A from the relay's 12V supply. The app notes on the
> 7805 spec sheet shows the basic regulator circuit.
>
> Good luck.
>
> - Keith Mc.
> --
> "Diode: What happens to people that don't die young..."
relays. There is a ton of information out there on relays, thanks for
clearing things up. I even see that Dontronics sells a kit that uses the
2003 and standard relays with a parallel port interface for only $9 without
relays. It think I'll roll my own just cause its more fun! Thanks again,
Dan
wanting to switch because your needs are going to be
different for each if it is inductive such as a motor
then sure you could use a realy but it will have a
short life span because of arcing across the realy
contacts in this case a solid state realy with zero
crossing makes the most sense zero crossing means it
turns on when the ac it at zero volts so there is no
arcing besides inductive loads can be very high start
current that qwickly goes down but that kick will
qwickly destroy a regular realy . goodluck
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<kenneth_m_73149@y...> wrote:
> you have to know exactly what type of load you are
> wanting to switch because your needs are going to be
> different for each if it is inductive such as a motor
> then sure you could use a realy but it will have a
> short life span because of arcing across the realy
> contacts in this case a solid state realy with zero
> crossing makes the most sense zero crossing means it
> turns on when the ac it at zero volts so there is no
> arcing besides inductive loads can be very high start
> current that qwickly goes down but that kick will
> qwickly destroy a regular realy . goodluck
checking the spec of the parts is good regardless of the device.
mechanical and solid state relays have 3 ratings. one for DC amps,
one for AC amps and one for inductive loads. The inductive load
rating will usually be in HP more so than amps. kinda misleading
with all the different type of motors available these days.
Dave