Review on SainSmart 101 70 102 8 Channel Relay Module by Jenny Mendez

Experience: Software developer, learning electronics with Arduino. My father EE told me about all current measurements. SETUP: - Connect Arduino 5V power supply to VCC - Connect Arduino digital ground to ground - Connect Arduino digital output to any IN1-IN8 - You're in business! CURRENT: I wired my meter in series and found that I am drawing 64mA through the Arduino 5V power supply and 1.9mA through the Arduino output pin. I flipped it and measured 7100 ohms at the coil, which means the coil is drawing 0.7mA at 5V, a bit low for me - for example I expected more than 19mA at the output, but seems 64mA at the power supply to be very reasonable. All eight relays draw 400mA as advertised. Note: Arduino's max supply voltage is 500mA on USB, so you're good there too. Pros: - It won't blow up your Arduino. - I didn't know this model had LEDs. I looked at the 4 relay model and the LEDs are bigger but they are smaller and work great. The LEDs in the circuit act like diodes. My father told me that when the field collapses on a DC coil, a negative voltage is created. If you don't have a diode, you can burn out the output transistor. It has NC (normally closed) and NO (normally open) contacts on the high voltage side. So if you want the light to be on or off by default, you can do that. There is a nice diagram on the board showing how the high voltage pins are placed. - Price - 4 mounting holes on the board if you need to screw it to something! - Have fun - you should buy one! CONS: - None / OTHER: - The pins on the header are really good, but I only have jumpers for the male layout and I need to buy a bunch of male and female jumpers at a radio store before I can hook this baby up to my Christmas lighting setup !