Author Topic: Irrigation control with relay switches  (Read 8252 times)

Offline verabp

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Re: Irrigation control with relay switches
« Reply #15 on: December 03, 2018, 03:26:05 pm »
The Fibaro RGBW looks useful so I ordered one (4 in / 4 PWM out @ 244 Hz).

As you likely know, one of the benefits of using 24 VAC instead of DC is that once the solenoid activates, the reactance increases which causes the current to drop to around 1/3 its initial value. Since the RGBW has PWM, one could design a parasitic RLC circuit to sit on each channel to achieve efficiency and overheating-avoidance benefits based on the same effect. Essentially a capacitor would be used to shape the PWM at 50% duty cycle into a pseudo-sinusoid to eliminate high-frequency effects. Did you play with this as well, adding the correctly sized cap would likely either improve your initial clamping current or improve solenoid lifetime based on what voltage specs you selected for drive and load.

Offline zedrally

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Re: Irrigation control with relay switches
« Reply #16 on: December 03, 2018, 05:36:28 pm »
^^^
I'd play safe and use a devices that is designed for use with 24V AC or DC.
For an out of box solution you can use a Philio PAN05 or ZWBCL2 which are ideal for this use and there are many in use in proven irrigation systems world wide.

Living in the Land of Oz, give me a vegemite sandwich. Home Seer, Vera Lite & Edge, Popp, Black Cat Smart Hub & Vera G, Black Cat Lite 1 & 2's a Black Cat Dimmer or 2, Fantem Tec and then some  Black Cat Cat's Eye PIR's & Door-Window Sensors, RFXComm, Broadlink RMPro & Mini plus a Z-UNO or 2.

Offline verabp

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Re: Irrigation control with relay switches
« Reply #17 on: December 03, 2018, 07:20:20 pm »
Thanks for the reply. I would like to propose the idea that installing the correctly specified RLC circuit to a DC-driven AC solenoid is in fact a safety precaution to reduce steady-state current. That is, I believe the rationale advanced above indeed does improve safety per your suggestion. For instance, such a design is absolutely less likely to overheat. Such overheating can cause grass fires-- I live in California and as such I do my best to avoid ignition sources both indoors and outdoors.

If one were to control irrigation solenoids with relay switches, I believe it is absolutely important for people to understand that a DC controlled AC solenoid does not feature the significant reduction in current once clamped, which can cause a variety of problems.

I'm new to the forum, is it within typical operating procedure here to suggest a link to your own product for sale without obviously disclosing it? Especially when commenting against a technical comment specifically intended to advance the considerations posed by those browsing this thread? Your comment feels a bit like self-promotion to me. From a quick read, there are obviously technically minded DIY'ers here, some of which may be professionals during their work lives whom may have already designed such an RLC circuit. I haven't gone through the details yet, and was hoping somebody might already have a favorite circuit in use. If I get around to it, I'll post a schematic.

Cheers

EDIT: For the record, after I posted this reply, you edited your post but did not call out your changes you made to your original text. This causes me additional concern since your stealth edit causes confusion which is not helpful. You may want to edit your post above again to at least repair your newly-broken sentence construction.
« Last Edit: December 06, 2018, 01:03:08 am by verabp »