Heater On Indicator Lamp

[Jay55]

Looked all over the forum for a circuit showing an indicator lamp across the input to the ssr from my 2352 pid. Struck out. All I want to do is have a 12vdc lamp light when the output of the controller triggers the ssr. Simple, right?
The output from the controller is 11vdc. The bulb measures 12 ohms. I assume I need a current limiting resistor in series so the bulb doesn't look like a dead short across the ssr input. Tried 10k which was too much. What should it be? Love this forum and have learned a lot from you guys.
Thanks.

 

[jeffmeh]

A better approach is to wire a 240v LED (assuming a 240v element) in parallel with the element. That will be a more true indication that the element is on or off. If you wire the lamp to the PID output, and your SSR fails on, your lamp could be off with power on at the element. This is a realistic scenario.

 

[BadNewsBrewery]

Another advantage to having the 240V LED in parallel with the element - if you are using a contactor or switch in your setup for mechanical disconnecting of the power (regardless of PID / SSR switching), you won't get your light turning on just because the PID is telling the SSR to fire. If you wire off the SSR input, your light will flash on and off constantly, even if the element isn't actually 'turned on', unless you go in and manually change the SV to be over the ambient PV so the PID doesn't fire.

Of course, this isn't what you asked so if you've considered the above and still think you want to go 12v LED... I'd say wire the LED in series with the SSR. So go PID -> LED -> SSR -> PID to complete the loop. The relatively minimal draw of the LED, and the wide working range of most SSR singaling voltages, shouldn't cause any issue. It'll also prevent the possibility of the dead short across the SSR input.

-Kevin

 

[Jay55]

Thanks guys. That's a good idea putting the led on the ssr output. I did that with an incandescent panel lamp and the bulb was always half lit due to ssr leakage. I wonder if the led will do that too? I'm just using the lamp to monitor when my rims element (120vac) is on, but you're right; if the ssr sticks closed for some reaon, monitoring the trigger isn't going to tell me anything. I was just bugged by the lamp being 1/2 on all the time. Seems like the led would do the same thing cause the 120 voltage is always there.
Thanks for your quick responses. I'll reconsider the output method instead.

 

[jeffmeh]

If you wire a 240v led in parallel to the element, you may get enough SSR leakage to illuminate the LED when the element is not plugged in. When the element load is there, it should work fine.

 

[alien]

I didn't know that Jeff. Do you know of a fix or workaround?

 

[evanmars]

Neon bulb?

 

[alien]

I like that idea, I might go with that. Should work with the right size resistor. 100K / 1W is about ballpark.

 

[jeffmeh]

I didn't know that Jeff. Do you know of a fix or workaround?

It's not really a problem that needs a workaround, if you just leave the element plugged in. Alternatively, you could wire in some type of resistor so there is always a load, but I don't really think it's worth the effort. I think there was a thread on here where someone did that.

 

[Jay55]

Your're right Jeff, there isn't a real problem. It's just a "more cool" thing with me to have the indicator lamp on only when the element is on instead of 1/2 on all the time and brighter when the ssr fires.
BTW, I found the thread with the resistor fix: in that scenario, it was a 240 volt circuit and the guy used a 5.7k 8watt resistor across the ssr output and it worked fine, providing enough load to keep the lamp off when the ssr wasn't being triggered. Think I may try 1/2 that for my 120 volt output. Or just leave it alone and let the lamp be 1/2 on Thanks for hangin' with me on this little non-issue.

 

[jeffmeh]

Jay55, I would feel the same way if the light is always on. With a 240v system, normally just having the element plugged in provides enough resistance to keep a 240v led off. On your 120v system, apparently having the 120v element plugged in does not accomplish that for a 120v led wired in parallel?

 

[BadNewsBrewery]

Has OP actually answered whether his element is plugged in during these tests? If I missed it, my apologies...

 

[Jay55]

No. The lamp stays on regardless. I went to Radio Shack Thurs. and got a 120v neon and threw that in. When across the output it lit 1/2 way, and when the ssr was closed, it went out. Wired it from hot to ground and it worked like an incandescent. Haven't tried an led yet. Maybe a 240 v led would work as you mentioned above, providing enough resistance to keep the light out. Problem is I don't have ready access to the type of led panel lights I've seen elsewhere in the forums with resistor and capacitor built into the unit. It'll continue to be a work in process. Gotta have something to tinker/obsess over or the wife will think somethings wrong with me The best indicator is seeing the mash temp going up when it should be stable, and my rims tube/2352 is very stable; never varies more than one degree, which I'm very happy with. Being out of the garage could be an issue, but I wouldn't see that either.