When using a transistor as a switch (which is how the driver to the relay is being used), one typically calculates things using a transistor gain of 10. You can get this figure in the transistor's datasheet under the "test conditions" for VCE(sat). So if the relay does need 90mA to latch then the base current needs to be 9mA, which isn't happening here.
Is it possible that the relay board was originally designed for a 9V or 12V supply?
Is it possible that the relay board was originally designed for a 9V or 12V supply?
Statistics: Posted by Mike**K — Tue Jan 06, 2026 6:58 pm