Specifying a relay

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Hi,

I'm looking for a couple (excuse the pun) of relays to control a
lighting circuit and a heater. The lighting circuit will be a load of
<1A, and the heater will be <5A, although I'm not sure if the heater
is purely resistive or not. Currently, I'm leaning towards an SSR, the
Crydom SDV2415R, but now I've been told I should buy a zero-crossing
version, particularly for the lighting circuit since random turn-on
can, apparently, damage filament bulbs.

So, I'm a little confused as to what I should buy. Also, I'd like to
be able to "dim" the lights - or, at least, to change them between a
few different levels from "mood lighting" up to full illumination.
(This will be based on a digital light sensor, but that's a different
subject entirely.) However, I'm not sure if an SSR can react fast
enough for me to use PWM (which my MCU can output natively) - I'm just
not sure which figure on the datasheet I should look for - and they
don't seem to have any sort of transient by which I could accurately
control the current allowed through/the voltage across the AC output
terminals.

So, perhaps what I need isn't a relay, but some other sort of
device...

I hope you can help,
Allan Lewis.

 

[ehsjr]

Hi,

I'm looking for a couple (excuse the pun) of relays to control a
lighting circuit and a heater. The lighting circuit will be a load of
<1A, and the heater will be <5A, although I'm not sure if the heater
is purely resistive or not. Currently, I'm leaning towards an SSR, the
Crydom SDV2415R, but now I've been told I should buy a zero-crossing
version, particularly for the lighting circuit since random turn-on
can, apparently, damage filament bulbs.

So, I'm a little confused as to what I should buy. Also, I'd like to
be able to "dim" the lights - or, at least, to change them between a
few different levels from "mood lighting" up to full illumination.
(This will be based on a digital light sensor, but that's a different
subject entirely.) However, I'm not sure if an SSR can react fast
enough for me to use PWM (which my MCU can output natively) - I'm just
not sure which figure on the datasheet I should look for - and they
don't seem to have any sort of transient by which I could accurately
control the current allowed through/the voltage across the AC output
terminals.

So, perhaps what I need isn't a relay, but some other sort of
device...

I hope you can help,
Allan Lewis.

Use a triac to dim the lights. Google "triac dimmer".
Ed