Connecting solar panel strings in parallel using relays

[RTSLVU]

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@rolfk wrote:

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@RTSLVU wrote:

The easiest way to drive DC relays with a DIO is to use an open collector driver IC or a small MOSFET.

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It depends what you consider a small MOSFET. The typical SMD types such as SOT-23 may actually be a little small for a 100VDC 20A contactor relay just as the simple TO-92 based MOSFETS may not be enough.

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Don't confuse a relays' contact rating with its coil ratings. I have several large contactors on our ATE systems that are contact rated at 900VDC 500ADC but only require 12VDC@120mA to close the contacts.

[santo_13]

Relay board like this https://www.makerfabs.com/4-relay-module-30a.html work off DIO signal levels as they have a MOSFET/Transistor to control the relay.

[rolfk]

I’m not confusing the contact rating with the drive rating. It’s just that large contacts usually require an adequate magnet coil especially if it is DC. You want the contact to close (and even more open) as quick as possible or your contacts have a very short life span.

You can select special low power contactors/relays but I wouldn’t count on any user to just have them laying around. And being warned and careful is always better than sorry. 😀