Good product with long delivery times

Good product with long delivery times

4 Channel 5V Relay Module Relay module for Arduino TTL logic

Customer Review

As Raspberry Pi hobbyists one is apparently always a little less favorably than the Arduino Group, because you have to make a few compromises on many available hardware. This relay module exactly, because actually it is designed for TTL level, not for the 3.3V GPIO of Pi.

For me, the relays switch but since over a month 8 times a day reliable, even without additional transistor before the optocouplers. I think this is also true for no particularly good solution, because that makes you look but the complete electrical isolation of the input circuit and relay supply again broken.

To wire: you have to remove the small jumper definitely, because that provides the connection between the input circuit Vcc (3.3V at P) and JD-Vcc of the relay circuit (5V) ago. The input circuit of the module is also realized a bit unfortunate, because the optocouplers are powered by the voltage between Vcc and the input ports, thus the relay are so low-active, ie operated inverted for GPIO signal.

In the input circuit and is still at each relay a light emitting diode. Should my relay no longer reliably switch, I'll just replace these LEDs by "0-ohm resistors" ;-) If the GPIOs of Pi are configured as inputs, then they are highly resistive and not provide enough power, so that the relay switch. However, the current is sufficient to allow the LEDs Funzeln to himself. Who cares, the has the GPIOs on which the relay depend equal configure after starting the Pi to pull up.

The relay module is the way by post from China. Therefore, it is so incredibly cheap and takes so incredibly long, until it is finally here.

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