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Customer reviews

4.8 out of 5 stars
4.8 out of 5 stars

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on 3 March 2017
Purchased unit in January to operate LED lights in the garage using a Raspberry Pi. Was very pleased initially, was easy to wire and mount. The LED's offer a good indication for the status. There has been a maximum mains current draw of 20W with about 2 switches a day for about 8 weeks and a relay has failed "on" with the coil still functioning but doing nothing. I have not opened the unit yet to see what the nature of the failure is but i find such an early failure of the relay disappointing.

2nd relay failed a week later, same failure, positive click but no contact change.
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VINE VOICEon 27 May 2015
These are really excellent little boards containing a pair of individually switched change over relays capable of handling up to 10 Amps on the switching contacts.
There may be morre than one version out there as one review refers to both red and green LEDs however this board only has red LEDs which indicate which input is operational.
There is a 4 pin header marked GND, IN1, IN2 and VCC. Gnd and VCC are self explanatory (if not then you should really not be playing with these sort of things!). IN1 and IN2 are the input pins which control the relays 1 and 2 respectively. Connecting either of the IN pins to GND (0 volts) will cause the relay to operate and the red LED for that relay to illuminate.
There is also a header marked JD-VCC, VCC, GND. This is supplied with a jumper pre-fitted connecting JD-VCC to VCC.


I can only assume that this header intended to allow you to supply the relays from another power source instead of your Arduino, Raspberry Pi, etc etc.
This is a good idea to ensure that you do not sink too much current from the 5V rail of the device you are connected to.

I have added the schematic diagram found on the web for further information.
review image
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on 24 May 2017
Spot on, just the job
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on 2 April 2017
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on 2 April 2017
good buy
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on 8 July 2014
This module contains 2 x 5 volt single pole changeover relays with screw terminals on the relay contacts and a 4 pin header strip for the controls.There are no instructions supplied and it is not immediately obvious how to operate the relays. The relay outputs are clearly marked with Normally open (NO1,NO2),Normally Closed (NC1,NC2) and common (COM1,COM2) terminals. The Header strip is marked Vcc,GND, IN1 and IN2. It is fairly obvious that 5 volts should be applied between Vcc (positive) and Ground (negative) and when applied the red LED lights up. However I had to check the circuitry to find that Vcc is connected to the Emitter of a pnp transistor and the relay coil to the collector and ground with a reverse diode and LED + 10k resistor in parallel with the coil. The header contact marked IN1 or IN2 is connected via a 10k resistor to the base of the pnp transistor. The upshot is that to operate either relay, IN1 or IN2 should be connected to the GND Header contact when the appropriate green LED will light. Each relay coil and corresponding green LED take approximately 75mA to operate at 5 volts.
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on 27 May 2014
Relay board works perfectly well with my Raspberry Pi. Because of the extra circuitry the board can be powered directly from the pi's gpio interface. I'm using it for boiler control.
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on 15 June 2015
For the money, these are pretty good value and work well at 5V. I did try them at 3.3V but they didn't want to stay "in" as it were. As others have mentioned, they need to have the jumpers set as follows:

jd-vcc->vcc DO NOT jumper VCC->gnd of you will fry the system. And probably your Pi/Arduino as well.

GND -> 0V
VCC-> 5V (or 3.3V if yo can get it to work reliably)
IN1 and/or IN2 when pulled to 0V (aka GND) by the Pi/Arduino will activate the relay and light the red LED.

PSM mentioned in this review http://www.amazon.co.uk/review/R3D0KG4S3E69JV/ref=cm_cr_dp_title?ie=UTF8&ASIN=B009P04ZKC&channel=detail-glance&nodeID=560798&store=electronics that the coild took around 75mA to work, including the LED. I thought he meant to actually make the relay click on, so I built a simple relay driver with a 2k2 resistor on the base of a 2n2222 transistor, with emitter to GND and collector to the IN1 or IN2 pin. When my Arduino pulls the digital pin high, connected to the 2k2 resistor the relay comes on. I figure this takes around 2mA to operate.

The Arduino (Duemilanova in my case) can handle 40mA - source or sink - on each digital pin, at 5V, so this is well within limits. The VCC can handle a maximum of 200 mA, so if the relay needs 75mA as per PSM, then I can probably run only 2 of these relays off the VCC pin. Be careful!

If you need more than 2, then best supply them off a separate power supply than from the Arduino.
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TOP 1000 REVIEWERon 21 April 2015
Had it hooked up to my Arduino Uno in no time. Bit confused at first as you have to take the input pins *low* to switch the relays from their default position. It turns out this is actually a good thing as the pins float high on the Arduino so there's no switching at startup. It's also a nice touch that there are two surface mount LEDs to tell you when the relays are switched.

Was also a bit confused as there is a jumper on the JDVcc and Vcc pins. Apparently this is because you can optionally drive the relays from an external power supply by removing the jumper and feeding the external supply to JDVcc. I've just left the jumper in place as the Arduino seems to provide enough current by itself.
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on 24 April 2014
The details are readily available on the Arpanet. If you are running off 5 volts with a micro-controller, leave the JD-VCC / VCC jumper in place, hook the VCC and GND to your system and wire up the IN1 and IN2 to your TTL outputs.

If you want to isolate the relays from micro power then power up from a separate 5 volt supply. This is the fully optically isolated feature.

Works A-OK!
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