Can I use Venus' built-in relay to control 5A 12V blower?
asked
Venus GX relay to control a 5A 12V blower
No, I think that is to much for the relay of the Venus.
But you can use the Venus relay to control a stronger relay that can drive the blower.
Thank you for your opinion, which is similar to mine. As I prefer to keep a circuit as simple as possible, I need the answer based on the data. In the Venus' datasheet, there is a limit of 6A 30VDC. I'm not an electrician, but I know that different types of loads have different properties and I want to be sure.
like matthias lange said, better use a power relay to protect your venus relay
dont forget to put a diode over the power relay coil to protect the venus relay contact
Just a clarification on your drawing. I have seen many contrasting drawings. In yours, you have the diode across the negative and positive wires.
According to some sources, with such a connection, the diode only serves as a "bypass" diode, not a "blocking" diode. Such sources say that for a blocking diode function, one has to connect the diode along the powered line (positive only).
Or is it the other way round? I'm confused.
F.
It's correct how the diode is placed and its "polarity", but this diode snubber type is used to protect the silicon junctions that drives the relay coil from reverse currents, which are killers for transistors junctions.
For protecting (relay) contacts, which don't care about the sense of the current, generally, an RC type snubber is used, across the switch / relay contacts.
Or to accommodate both, use an RCD snubber. Which might be overkill... :-)))
@Alex Pescaru
Clear. I'm assuming that the logic is the same when using an external solid state relay or any other type?
F.
Hi @Suavek
While the datasheet values are in range for your application, switching 60W through a small relay will not provide a long life for that relay.
The problem is the DC arcing, that is bigger and bigger as the load increases.
Successive arcing during time will lead to a slow destruction of the relay contacts and sooner than later the contact will either melt or fuse together.
Here's below a graph for seeing the cycle life of a high power DC contactor from Tyco.
You can clearly see, the greater the current (power), the less switching cycles.
So, if you want to protect something that's inside and difficult to replace, switch an external relay which is easier to replace.
Alex
@Alex Pescaru and @Duivert NL, sorry to come back to you and for hijacking this thread but I think the OP will find this information useful.
Looking at the Amazon US site again, all the listed manufacturers say that their diodes should only be connected inline the positive side only (see attached photos). My tentative conclusion is that the wiring depends on the manufacturer. I searched for "schottky diode" and for "blocking diode". It seems Americans don't use the term "snubber".
Second question: which specific one would you pick? It seems the MD is an overkill. Its specs and link below. The second one has less capacity but it is cheaper. Link also attached.
1. MD
2. Generic
Hi @Fideri
I believe that you / we are talking of different things.
Those diodes you are talking about are for combining / isolating DC sources or bypassing PV panel elements when shading occurs.
They are high power/current diodes, not like those used for induction protection.
Like these from victron: https://www.victronenergy.com/battery-isolators-and-combiners/argo-diode-battery-combiners
Alex
That's clearer. To be on the cautious side, I will buy 2 diodes and wire one in parallel and the other in series, if it has no negative effect. I know one of the diodes will be redundant but that is fine by me.
F.
