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  1. #1
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    Suggestion of relay for controlling FPGA

    My uncle is making his own smoke house, and to make the smoke he decided on using a water heater element. Over the Easter Day we were discussing this, and it gave me the idea for my final project. So, my final project will be creating a controller/display for a water heating element. The goal is to use the DE0 to control the power source to the heating element, so that the wood chips used for smoking, will burn and smoke but not catch fire.

    Thermocouples will be connected between a DE0 (on the GPIO header) and the water heating element. The DE0 will read and display (the later on a 16x2 LCD add-on) the temperature of the heating element. The power source for the heating element will be connected to a relay and the control of the relay will be connected to the 5v pin on the DE0’s GPIO header. Upon flipping a switch on the DE0, a LED light will turn on, indicating that power is being sent to the relay and that the element has power. Once the heating element has reached the desired temperature a 15-minute timer will start. This timer will be displayed on the LCD. Once this 15 minutes has passed, the 5-volt signal going to the relay will be cut, the LED turned off, and a new timer will be set for 15 minutes. Once this 15 minutes has passed, the heating element will be given power and upon hitting the desired temperature a 15-minute ON timer will be set. This sequence will be repeated until the original switch is flipped off, or until 4 ON-cycles have passed.

    As for reading the temperature of the thermocouples I have found that I will require a digitize of sort. This is what I have picked out, MAX318551(http://www.kynix.com/uploadfiles/pdf...2bT_905711.pdf). My concern is the relay. I am not sure if I am understanding the terminology correct.

    What I need is the 5v GPIO of the DEO to send the 5 volts to the relay when called. I am correct in thinking that this particular relay requires 5 volts to turn on and can pass upto 220volts?


    If I am correct, is there anything special I should know about hooking up it at the FPGA?

    Lastly, does anyone have a recommendation of relay for my needs?
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    •   Alt18th April 2017, 11:17

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  2. #2
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    Re: Suggestion of relay for controlling FPGA

    Draw a schematic of your circuit.
    I strongly suggest you use a buffer to power the relay.



    •   Alt18th April 2017, 13:42

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  3. #3
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    Re: Suggestion of relay for controlling FPGA

    Hi,

    A relay is mainly specified by:
    * Load current
    * load voltage
    * coil voltage
    * coil current
    * isolation voltage

    These values are urgent to know to find a suitable relay.

    ***
    I assume you think about a mechanical relay.

    To reduce EMI .. I recommend to use solid state relay with zero cross switching.

    Klaus



    •   Alt18th April 2017, 16:21

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  4. #4
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    Re: Suggestion of relay for controlling FPGA

    Won't the water heater element reach high temperatures within a few seconds?

    Are you sure you don't want a shorter on/off cycle time similar to what an oven might have?



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