Relay Purchase

Started by c04203420 October 11, 2005
Im about to make a bid on ebay for some cheap solid state relays. The
details are:

OPTO 22

Manufacturer Part Number: MP240D4
Description: RELAY, SOLID STATE 4A; Voltage, load RMS min:24V;
Voltage, load RMS max:280V; Current, load:4A; Current, surge:85A;
Voltage, control DC min:3V; Voltage, control AC min:24V; Voltage,
control AC max:280V; Voltage, control DC max:32V; Output type:
Thyristor; Voltage, isolation:4000V; Current rating:4A; Current,
leakage:5mA; Current, surge single cycle:85A; I2t:30s; Temperature,
operating (a) max:100C; Temperature, operating (a) min:-40C;
Voltage, control pickup:3V; Voltage, dropout:1V

My question is this. Would this power a high output fluroescent lamp
equipped with built in ballast. The load is (240V @ 110watt)

Reply soon. I only have 20 hrs to get my bid in.

Thanks in advance.

Marc.



Yes. The average current for 110watt at 240VAC is 110/240 = 0.46Amps c04203420 wrote:

> Im about to make a bid on ebay for some cheap solid state relays. The
> details are:
>
> OPTO 22
>
> Manufacturer Part Number: MP240D4
> Description: RELAY, SOLID STATE 4A; Voltage, load RMS min:24V;
> Voltage, load RMS max:280V; Current, load:4A; Current, surge:85A;
> Voltage, control DC min:3V; Voltage, control AC min:24V; Voltage,
> control AC max:280V; Voltage, control DC max:32V; Output type:
> Thyristor; Voltage, isolation:4000V; Current rating:4A; Current,
> leakage:5mA; Current, surge single cycle:85A; I2t:30s; Temperature,
> operating (a) max:100C; Temperature, operating (a) min:-40C;
> Voltage, control pickup:3V; Voltage, dropout:1V
>
> My question is this. Would this power a high output fluroescent lamp
> equipped with built in ballast. The load is (240V @ 110watt)
>
> Reply soon. I only have 20 hrs to get my bid in.
>
> Thanks in advance.
>
> Marc. > >. >
>




OPTO 22 Manufacturer Part Number: MP240D4
Description: RELAY, SOLID STATE 4A; Voltage, load RMS min:24V; Voltage,
load RMS max:280V; Current, load:4A;

My question is this. Would this power a high output fluroescent lamp
equipped with built in ballast. The load is (240V @ 110watt)

Reply soon. I only have 20 hrs to get my bid in.

=============
Marc,
Yep, perfect, what it was made for. New price seems to be $10-12 in
small qtys.

Cheers
lauren



While solid state relays with isolation can be purchased up to 40amp
at 240VAC, they have problems with induction - motors and ballasts
can create EMF that is destructive.

Mechanical relays may be a much better choice as the mechanical ones
usually fail in an 'OFF' mode. Whereas, the literature that I've
seen says the SSRs more often fail in a short circuit mode.

Additonally, you can easily configure a Double Pole Switch for a
complete off with the mechanical. SSRs are usually single pole.

Solid State Relays generally produce 1 watt of heat per amp. This
needs to be included in your design.

I really cannot think of many good uses for them aside from creating
an excellent programed timer for your home's Water Heater. That load
is resistive, generally on its own circuit breaker, and you can
usually install a protective cover around them and the water heater
is usually in a special place.

You can enhance the SSR's fuction by including a capactor and
resistor across the load, but induction will always be the 'enemy' of
switching. Solid State seems to suffer more as there has been a long
evolution and development of high quality, powerful relays before
solid state came into use.

Always design your safety features first. It certainly will provide
you with less downside.

--- In basicx@basi..., "c04203420" <c04203420@y...> wrote:
>
> Im about to make a bid on ebay for some cheap solid state relays.



> ... I really cannot think of many good uses for them...

SSRs are great for phase control; if switched on at an appropriate time
in each AC half-cycle, they can smoothly change the average power
delivered to a load, like varying the intensity of a lamp, the speed of
a motor or the temperature of a heater. SSRs are also silent, sparkless
and bounceless, and can operate from logic levels. Mechanical relays
cannot compete with these features. Tom



--- In basicx@basi..., "G. Kramer Herzog" <hwanghetw@y...> wrote:
>
> While solid state relays with isolation can be purchased up to 40amp
> at 240VAC, they have problems with induction - motors and ballasts
> can create EMF that is destructive.

You can go a lot higher than that anymore. I designed Controllers
using 3-Phase SSr's for large Dish Antenna's. 2 SSR's would control
the forward and reverse of one motor. I have not had any problems. I
do always put a 3 second delay between Fwr and Rev even if the button
was depressed. I have designed Christmas lights that dim, flash or
come on bright using this Microprocessor. They have been working for 3
years now.

Ken Smith



--- In basicx@basi..., Tom Becker <gtbecker@r...> wrote:
>
> > ... I really cannot think of many good uses for them...
>
> SSRs are great for phase control; if switched on at an appropriate
time
> in each AC half-cycle, they can smoothly change the average power
> delivered to a load,

The do work very well from a microcontroller with a 2n2222. [I have
one I tried out for a few weeks with a BX-24. But, I used a 100 watt
blub with a 10amp SSR.

I am confused though. Isn't that a Triac the usual phase control
circuit and not an optically isolated SSR?

I am just passing along what I read in technical summaries gleaned
from the internet as people might try to put several in their house
wiring circuits without any reservation to gain central control. I
wouldn't use one with a refrigeration unit or central air conditioner
unless I had encouraging documentation or an expert engineer
assisting. I would be happy to e-mail the whole HTML to anyone who is
concerned.

After thinking about the 40 amp SSRs, I guess they work well with
halogen and sodium lighting [big street lights]. That would explain
why they are made. There is debate about using them with motors and
ballast.

I personally like them, but am a bit wary of using them for robotics
because a runaway motor is a significant problem. With the Double
Pole, at least one side has a better chance of switching down if the
contacts fail in an on position.



> Isn't [] Triac the usual phase control circuit and not an optically isolated SSR?

The switching device in an SSR _is_ a triac. A standard puck-style SSR
contains a triac on a heatsink, an optocoupler and some gate-control
circuitry that either switches the triac immediately or at the next
zero-current point.

An SSR is a module of convenience that contains other components; if you
needed to, you could assemble one from discrete parts. Tom


Debates are nice but on the spec sheets it does say that it will work
fine with HID ballasts so im assuming the fluro ballasts are good to
go too.

All i need to know is that im not gunna kill myself or blow my
microcontroller up...

What you were discussing is alien to me. Im relatively new to
electronics so im still in the researching like mad stage so to speak.

Your replies are still apreciated though. Thanks a lot.


> All i need to know is that im not gunna kill myself...

We can't be sure. You are in the red zone and you are an amateur.

Truly, controlling AC loads is a dangerous detail. Done right, it is
perfectly safe. Done wrong, it can be really fatal or worse; it can
burn your house down after it kills you.

Minimally, you must do two things:
- isolate your electronics from the AC power line and the load,
- encase the high voltage circuitry to prevent accidental contact.

If you mount an SSR in a grounded metal box below (or in, if there is
room) the lighting fixture and use sound wiring to it, you should be
safe. If you are unsure, though, get local help with this part of
your project. Tom