Gravity: Digital Relay Module (Arduino and Raspberry Pi Compatible) (DFR0473)

Support Product Questions
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This is a placeholder topic for “Gravity: Digital Relay Module (Arduino and Raspberry Pi Compatible)” comments.

Introducing the Gravity Digital Relay Module – the latest addition to DFRobot’s Gravity series! This module is a little different to the other relays in our store…

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Looking at the labelling on the relay shown in the pictures here and on DFRobot’s DFR0473 product page, we see 10A 250VAC, and in fact the spec sheet https://raw.githubusercontent.com/DFRobot/DFRobot_3V-Relay-Module/master/HF3FD_en.pdf even seems to indicate Max switching Voltage 277VAC/30VDC

So, is the specification

  • Max Switching Voltage: 35VAC; 30VDC
  • Rating Load: 10A@35VAC; 10A@28VDC
    maybe an error ? Or would it be other components on the board which impose the limitation ?
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From the actual relay data sheet

image
image610×286 43.4 KB

Don’t know where the other numbers come from. Looks like a direct copy but not from the data sheet obviously.
Cheers Bob

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Thanks Bob, I hadn’t noticed DFRobot was pointing to a copy of the spec sheet … but it looks the same to me, so what have I missed ?

And does that answer whether to go with 250VAC or 35VAC ?

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Most relays of that style will switch 250V AC or about 28V DC. I am not familiar with that make but Omron (well known brand) do.
The difference between ACV and DCV is the arcing and metal migration. You can switch a much larger AC voltage than DC.
Cheers Bob
Add on, I missed this bit

Core and DFRobot say max switching is 35VAC. The data sheet says 250VAC

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That was my original question.

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Hey @Donald23173,

35VAC is the rating for the module as a whole.

While the H3F3FD Relay datasheet might rate it for 250VAC, the traces, connectors and other components on the board will bring this rating down to 35VAC to avoid damaging the more delicate parts of the system.

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Hi Jane
I think there is a safety issue as well. This rating tends to keep people handling and mixing 240VAC with all the low voltage bits. Good idea actually. Removes any possible liability claims on the manufacturers.

In practice most of these types of boards have the relay mounted 90º different to this one so the NO and NC contacts are only a very few mm from the terminal block and the common is a few mm longer down the centre line of the pins with minimal low voltage points anywhere near them.

All up though this Forum and all associated bits is really aimed at the hobby market and I do note that Core should be given full marks for actively discouraging inexperienced people to go anywhere near mains 240VAC wiring. Putting ratings such as this on complete modules goes a long way to achieve this.

I think that sometimes the descriptive text regarding this sort of module could be a bit clearer to avoid confusion where people see one spec on the complete unit and another quite different spec on the major component.
Something along the lines of
“Even though the relay data indicates a switching capability of 250VAC this unit is rated at a switching voltage of 35VAC”
Or something along similar lines.
Cheers Bob

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Hey @Robert93820 ,

Thanks for the note! I will pass it on to our team, who should have the page updated shortly to attempt to avoid this form of confusion in the future.

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Thanks Jane for confirming; that was what I was expecting.

i thought it worth confirming since occasionally a spec sheet or web page is copied from a similar product and not all the details get changed :wink:

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No worries, Donald, always better to be safe than very, very sorry. :stuck_out_tongue: