Re: OT: SSR questions

Maybe something like a 7W night light bulb. This would double as an
indicator lamp so you'd know when the element is on.

http://www.source4lights.com/product.aspx?prod=148&bbaff=6250094


"Phil Paintin" <charneybarn@xxxxxxxxx> wrote in message
news:1151231971.517899.295350@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Jeff Davis - Charter wrote:
On 6/24/06 7:58 AM, in article
1151153905.367229.104550@xxxxxxxxxxxxxxxxxxxxxxxxxxxx, "Phil Paintin"
<charneybarn@xxxxxxxxx> wrote:


Jeff Davis - Charter wrote:
I was trying to PID my electric smoker using only parts I had on hand:
cheap
PID controller with 5 vdc ssr output, 30 amp power relay with 120v
coil and
5 amp ssr with 5 vdc input and 120 v output.

I knew my 5 amp SSR was not enough to handle the 13 amp load from the
heating element in the smoker so I tried using the 120 v output from
that
SSR to control the power relay. However (I guess) the power relay coil
was
not enough "load" and the SSR would not turn off the relay.

Ultimately I connected a 15 watt glue gun in parallel with the coil on
the
power relay and everything worked fine.

My question is, how much load do I need to make the SSR switch and
would a
power handling resistor work as well? Although I don't currently have
a
better use for the glue gun.

Or is there a better solution I can implement using my existing parts?


Jeff, do you have the make and model of the SSR to help with looking up
the specs ?

SSRs don't like inductive loads (like the coil of your mechanical
relay) in general, and the manufacturer will probably recommend using
an R-C 'snubber' network, at least with larger inductive loads. Not
sure what the situation is with small inductive loads . . .

Phil, It's an Omron G3NA-210B. What's an R-C snubber?

A snubber network is a small resistor + capacitor circuit supplied as a
module to connect across the output of SSRs to damp out the current
surges when switching off an inductive or capacitive load. These
surges are what cause the sparking across mechanical relay contacts
when they try to break the current to switch off a load. Omron don't
mention one for this unit.

Your relay is apparently 10 amps capacity, though that doesn't change
anything here. Omron quotes a leakage current of up to 5 mA which
might be enough to keep the mechanical relay coil energised when
combined with the fact that it's an inductive load.

The cleanest solution would be to just get a higher current SSR on ebay
-- 25 or 40A. If you don't want to buy anything else but do want your
glue gun back, a low-wattage lamp would do in its place.



.

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