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deapsquatter

Victron Venus Relay with solid state relay.

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I got one of these to attach to the VenusGX as I want to control when my Hot Water Geyser comes on. Any tips to wiring it up? From what I can tell I need to use a 12V Power supply connected inline with the Venus relay. When the Venus relay is activated the 12V will activate the solid state relay and vice versa. Anything else I need to do? I tried a test run and it all worked fine except when the Venus relay was OFF the 12V power supply was making a clicking sound over and over.

image.thumb.png.c051a2b0d744b7368615d7ad9a0ea800.png

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Both plans presented here seems fine. I don't know why the PSU would be clicking... what kind of clicking are we talking about? I know that some of the SMPSes in my house make a high pitched hiss when you unplug the load. That's because there is no load and the SMPS has "cycle skipping", so you hear the skipping. Normally an SMPS runs at  frequency too high for humans to hear.

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2 minutes ago, plonkster said:

Just don't overload it 🙂

So no idea what that little relay draws in my photo above. I'm assuming it just needs something small to tell it to switch on and off.

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2 minutes ago, deapsquatter said:

Hmm - so using the 5V power out and turning the relay on actually reboots the the Venus GX ☹️

A solid state relay is usually a TRIAC with an opto-isolator on the gate, and it needs a few milliamps at most to operate. Perhaps use a separate 5V supply (or the 12V one and actually measure it). But the Venus device rebooting suggests that you overloaded the 5V supply.

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Posted (edited)

Actually I'm probably wiring this totally wrong. No idea what I'm doing 😀 Cable to left is connected to nothing at the moment. Venus reboots the moment I plug in the Relay and 5V power plug (nothing other end)

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Edited by deapsquatter

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1 hour ago, deapsquatter said:

Removed it  - the plastic housing started to melt ☹️

Was the SSR mounted on a suitably specified heatsink ?

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3kW elements are a heavy load in a domestic setup.  The 7 day timers that switch electrical loads also take strain when switching this kind of load (despite claims from the manufacturer they can handle it)

The only time when one has to use a SSR is when the on/off switching is quick. Contactors aren't a good option in these applications

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4 hours ago, Sean said:

Was the SSR mounted on a suitably specified heatsink ?

Indeed. Cause internally it is usually a TRIAC, and those things have a voltage drop and a bit of series resistance. For example, here is the spec for a fairly common TRIAC:

Selection_541.png.2eb1339adef7a625f0454db5cb6ce239.png

You can see a fairly constant voltage drop of between 0.7V and 1.1V, depending on temperature, and an additional resistance of around 0.25Ω on top.

So your average 3kW geyser at around 13A, gives a good 4.something Volt drop and will generate a good 60W of heat in the process. So I'd probably not want to use this particular triac for the job then...

Most TRIACs will have at least that voltage drop, so at 13A you will have a good 15W or so of heat to put somewhere (at the very least). This is where you then need to consult the specification for the thermal resistance, and if  that is in spec, then you can do some more math to determine how much heatsink you need to put on it (heatsinks are rated in °C/Watt), and then you need to keep that thing below 125°C.

Long story short, the aluminium base of most SSRs is way too small.

Here was a more practical setup that I tried once. I used the "master valve" output of an irrigation computer (24VAC) via an opto-triac to start the well pump. I used scrap material, all of this came from other things, even the aluminium. This thing ran at a good 70°C... for an 850W pump.

It died some weeks later when water got into it and it burned a big hole through the stripboard... After that I scrounged a 24V relay from the scrap pile (used to be from a garage door opener) and used that instead.

triac1.thumb.jpg.1666eac507c50c2a3f4add6e99120045.jpg

triac2.thumb.jpg.8b9382ecffcf037b7d00049840079bae.jpg

 

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9 hours ago, plonkster said:

After that I scrounged a 24V relay from the scrap pile (used to be from a garage door opener) and used that instead.

Another good idea to find relays is to strip them from those silly 600VA UPSs. (If anyone wants one I have a collection)

Din rail contactors are quite pricey but are the way to go if you want to do a proper job.

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The SSR switching voltage is 3 to 32VDC, I think the heat generated might be due to the low switching voltage of 5V if a higher voltage of 24V or even closer to the 32V was used I think the heat might be less as the gate opens more to let more current through (reducing the resistance) Please correct me if I am missing the plot, but I think theses SSR’ are normally driven through a temperature controller that pulses 3V for low heat and pulses 32V for high heat.

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Posted (edited)
26 minutes ago, Gerrie said:

The SSR switching voltage is 3 to 32VDC, I think the heat generated might be due to the low switching voltage of 5V if a higher voltage of 24V or even closer to the 32V was used I think the heat might be less as the gate opens more to let more current through (reducing the resistance) Please correct me if I am missing the plot, but I think theses SSR’ are normally driven through a temperature controller that pulses 3V for low heat and pulses 32V for high heat.

No sir! A triac is a back to back thyristor (see Plonksters last post)

A thyristor either switches or it doesn't. The gate needs a certain voltage to get the thyristor to switch. (once the device switches it conducts until the voltage across the device reduces to 0V) They are good at what they do but still have their limitations.

Why Deapsquatter decided to use a SSR I don't know. It's not the ideal solution for this application. But despite all the evidence he continues down this path trying to justify his reasons for using it..

I have listened to claptrap on other forums such as My Broadband. I don't think this site needs to emulate that one! 

 

 

Edited by Richard Mackay
Clarity!

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34 minutes ago, Richard Mackay said:

A thyristor either switches or it doesn't.

Thanks for clearing that, I had to do once with a high temperature lab oven that worked with these SSR’s and I did not quite understand the working of them although I noticed when the oven reached the set temperature the little light on the SSR would flash, about once every three seconds and if it needed to increase in temperature it would pulse faster and faster, sometimes permanently on till it reached the set temperature.🙂

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Posted (edited)

Just to add a bit more. The input voltage doesn't switch the Triac directly. The input voltage lights up an LED, inside a little package called an opto-coupler or opto-traic (the photons emited by this device pushes the other side into conduction). In my photo above, that's the whitish package with the MOC part number. The other end of the opto-triac then switches the real triac (the black 3-legged thing in the TO-220 package).

So the SSR probably incorporates a small linear regulator that operates from 3V-32V, and this powers the LED inside the opto-coupler. This means a really low current is required (under 10mA) to switch it on, since all you need is to light up a LED.

(My hacked-together circuit above simply uses a 3.3k resistor to drop the 24V to something suitable and naturally does not have the same range).

Since it is doubtful that the makers would have bothered with an SMPS to get the wide input voltage range, a lower voltage will likely be better. 5V at 10mA means you need to drop 3V (aproximately) to get it down to a good voltage for the LED, at 10mA, that is 0.03W of heat.... which is nothing. But as you push it up to 32V, it's 0.3W, which is beginning to be something... 🙂

 

Edited by plonkster

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