Best Relay-Follow up
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Hi guys,.... thanks for the answers. The corrosion on the relays are not from outside environmental causes, what I meant was which relay is less likely to corrode from the inside, that is carbon buildup due to constant micro spark contacts when relay is activated. What is the deal on solid state relays? any model number you recommend ? price?
thanks all... basil
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thanks all... basil
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Comments
help if the circuit design will allow it. Maybe the load is too big. take
into consideration the instantaneous peak amps of the load. Especially for
an inductive load. Sometime relays corrode because of unlike metals. the
wires, screws, contacts all have to be made from the same metal or they
will corrode over time. battery cables are a good example. Several months
ago got this job of restoring a 60 year old RF generator. In the process, I
completely took apart the mechanical relays and filed the contacts. Then
sprayed a Zinc coating on them to keep them from oxidizing. This is the
same method I use on my battery terminals to keep from corroding.
a solid state relay is kinda like a power MosFet with an opto-isolator
gated input. It takes only 3Vdc / 10ma thru a current limiting resistor to
control large currents on the output. a BS1 will easily directly drive a
SSR. but careful not to overload the ouputs. The BS1 see's them as LED's.
Those that know me know I'm somewhat partial to the BS1 because its small a
SIP package, inexpensive, and simple.
the disadvantage is a small current of a few ma has to be maintained on the
load side. the advantage is no diode is required since the SSR doesn't have
a coil. Also the load can be AC or DC. doesn't mater.
Some other members may be able to give a explanation much better than I
can. mine only comes from personal experience.
my SSR of choice are the Opto22 models. The 25A models work fine for
switching heavy loads such as solar array panels.
Opto22 MP240D4-17 240V / 4 A
Opto22 240D25-17 240V/ 25A
some other vendors of solid state relays are
International Rectifier Crydom D2440 240V / 40A
CrouretGordos G280D25-49 280V / 25A
"AllElectronics.com" has the above two for around $11
At 07:40 PM 5/16/2004, you wrote:
>Hi guys,.... thanks for the answers. The corrosion on the relays are not
>from outside environmental causes, what I meant was which relay is less
>likely to corrode from the inside, that is carbon buildup due to constant
>micro spark contacts when relay is activated. What is the deal on solid
>state relays? any model number you recommend ? price?
>thanks all... basil
>
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>Do you Yahoo!?
>SBC Yahoo! - Internet access at a great low price.
>
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<basilmelbourne@y...> wrote:
> Hi guys,.... thanks for the answers. The corrosion on the relays
are not from outside environmental causes, what I meant was which
relay is less likely to corrode from the inside, that is carbon
buildup due to constant micro spark contacts when relay is activated.
What is the deal on solid state relays? any model number you
recommend ? price?
> thanks all... basil
The arcing is from the relay opening. As the gap closes, it must
close the two contacts until the gap can be bridged by the voltage,
by the time that occurs, the gap is still closeing and the contact is
made.
But, as the contacts open, the arc will continue for much greater
distances and that is where the wear occurs.
google lugoswr.mpg and watch just how wide arcs can go.
If you expect to damage relays, use silicon. Triac, MOSFET or some,
device that can handle ratings.
Dave
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> Do you Yahoo!?
> SBC Yahoo! - Internet access at a great low price.
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