How can the maximum amount of current be determined for the relay contacts?
An easy way to determine the limit of a relay is to multiply the rated Volts times the rated Amps. This will give you the total watts a relay can switch. Every relay will have two ratings: AC and DC. You should determine the AC watts and the DC watts, and never exceed these ratings.
How much voltage does a relay need?
Most are rated at 12v, usually a range of 12-15v. Actual voltage required to operate the relay is usually a little under 12v. That is why your accessories can still operate with the key on and engine off, usually making actual voltage a bit under 12v with lights on.
Will an AC relay work with DC?
Edit: As Andy says, an AC relay will work on (greatly reduced) DC. Of course you can also make a DC relay work on AC by adding stuff to it (if you use a capacitor filter you might need only 18VAC (RMS) to operate a 24V relay, and 24VAC would cause it to overheat and fail early).
How does a positive output relay increase output time?
The capacitor allows the coil of the relay to be energized until the capacitor stores a charge, thus de-energizing the coil. The resistor bleeds off the charge of the capacitor when positive voltage is removed from the other side of the coil. You can increase the output time by simply changing the value of the capacitor.
Can a relay module be used with an external power supply?
(1) Usually if an external power supply for the relay module, it is important to short the Arduno/Rpi signal ground with the external power ground, so that Rpi signal has the common ground with the external power supply ground.
Is the relay module always off on Arduino?
One important clarification is that whether a module is High or Low triggered, if the Rpi/Arduino is not powered, or if GPIO pin is in input mode in booting or otherwise, then no current drives or sinks to activate optocoupler, relay is always off.
Can a relay module be connected to a RPI?
A case with Rpi powered by a battery, the Rpi’s ground can be “floating” and not connected electrically to the relay module. The OP’s 4 channel relay module is “Low Logical Level Triggerable” (Low Trigger) with the “JD-Vcc jumper” to suit different configurations of relay power and control signal levels.