Relay switch problem

MarkCrCoMarkCrCo Posts: 80
edited December 2017 in BASIC Stamp Vote Up0Vote Down
I'm trying to make this relay work but I either get the relays' LED to light with out activating the switch or I short out the stamp and it resets when the pin is set low. The only docs I have refer to the raspberries' 3.3v output so I made the modifications to the resistors as noted.
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  • Beau SchwabeBeau Schwabe Posts: 6,339
    edited December 2017 Vote Up0Vote Down
    Does the relay board have an internal pullup resistor?.. If not you may need to add something to the Collector of the transistor.

    I dont get that the stamp shorts out. Something isn't connected right. With the circuit you have there should never be a short condition.



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  • https://www.sainsmart.com/products/8-channel-5v-relay-module

    This also is my first Basic stamp from many years ago that I use for testing various ideas. Maybe it has out lived its usefulness. I think I may try another stamp.
  • I'm pretty sure I don't understand this relay. I thought if the input was pulled to ground it activated the switch on the relay. I've tested that by connecting it directly to ground and I still get the LED lit - which I learned since it is red means Error - and no change in the switch. Any explinations or help in setting this up would be appreciated.
  • The first review on the Sainsmart site for this relay board:
    GREAT PRODUCT
    Karl on Nov 16, 2014
    This is a fantastic product at a great price. Just one thing! Do NOT set the jumper to GND-VCC! This will cause a short! This is not a design error! You can use the board non-isolated the way it comes.
    This jumper is used to separate the opto-coupler circuit from the relay side.
    To fully isolate the inputs from the relays:

    1) Pull the jumper and use secondary 5 volt power to the relay using GND and VCC next to JD-VCC. Do NOT use the VCC and GND pins next to the IN1 and IN8 input pins!
    2) The JD-Vcc is the common for all inputs. The input side consists of the indicator LED and opto-coupler-LED and a 100 ohm resistor in series.
    3) Apply Arduino 5 volt to JD-VCC and IN1 or INx to the Arduino outputs (LOW) and the relay will be triggered. Hope this helps! Thanks to Eric for the schematic! You can find a schematic on amazon.
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  • Well no one actually caught the mistake in my original question. My original question was why it didn't work when I made the modification to the resistors to adjust for the difference from the raspberries' 3.3V output to the Stamps 5v output. The problem was that the raspberry does out put 5V so no modification was needed at all.
    Connected vdd to vcc next to the input connections, Connected vss to the ground on the relay board. Left the ground next to the input pins open and left the jumper in place and with the original resistors from the diagram it works.
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