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Hack to interface a Mighty Mule Driveway Alert to HS4 using Z-Wave

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    Hack to interface a Mighty Mule Driveway Alert to HS4 using Z-Wave

    Project: Interface a Mighty Mule Driveway Alert magnetic vehicle detector to a Z-Wave sensor to provide HS4 notification of vehicle detection.

    We have a long driveway and wanted to receive a Z-Wave alert when a vehicle is approaching. Using an IR motion sensor provided mixed results: sometimes vehicles would go undetected, and there were frequent false alarms from animals, especially at night. Various cameras produced similar unsatisfactory results.

    Determined to find a more reliable indication of an actual vehicle approaching, I installed a buried electromagnetic sensor, the Mighty Mule Driveway Alarm. That system includes a receiver that beeps when the metal mass of a vehicle passes. It seems to detect vehicles almost 100% of the time, with no false alerts from animals. Unfortunately, the receiver offers no ability to interface with HS4. Time to hack.

    After some trial and error, I found that with a bit of work the receiver can be directly interfaced with an Ecolink Z-Wave Plus Door & Window Sensor, which provides a set of screw terminals for activation from another device.

    This hack has been working flawlessly to trigger HS4 events for several months. However, it is an experimental setup constructed without any schematics or other information on the nature of the circuitry in the Mighty Mule receiver or Ecolink sensor, and manufacturing changes or other variations in either device may prevent proper operation.

    This hack requires a fully functional Mighty Mule Driveway Alarm installation, including digging a trench and installing the Mighty Mule sensor and transmitter per the manufacturer's instructions. This hack will only work if the system properly detects a vehicle by sounding the alarm and turning on the "VISITOR" LED prior to making any modifications.

    IMPORTANT: This modification requires soldering to the Mighty Mule receiver, thereby voiding the warranty. It is important to be satisfied with the operation of the Mighty Mule standard alarm before proceeding.

    Items required:
    1. Mighty Mule FM231 Driveway Alarm (about $65 on Amazon, receiver unit shown in Figure 1)
    2. Ecolink DWZWAVE2.5-ECO Z-Wave Plus Door & Window Sensor (about $30 on Amazon). The sensor includes a larger transmitter (Figure 2) and a smaller magnet; the magnet is not used in this project.
    3. Wire cutters, soldering iron and solder
    4. Approx. 6" length of two-conductor small gauge flexible wire of different colors or otherwise individually identifiable
    5. Optional double-sided foam tape to hold together

    The Hack:
    1. Trim 1/8" or so of insulation from both ends of the wire pair
    2. Remove the plastic feet filling the four holes on the bottom of the Mighty Mule receiver, and remove the four screws
    3. Carefully remove the circuit board, being especially mindful of the antenna, which is attached to the board by a wire
    4. Following Figure 3, carefully solder one end of the wire pair to the spots labeled "A" and "B" on the circuit board and note the color of the wires attached to each
    5. Run the wires through the mounting hole in the back of the receiver and reassemble the case
    6. Remove the Ecolink transmitter switch cover by pressing on the top release and pulling apart
    7. Following Figure 4, run the unattached wires through the slot near the terminal block and attach to the block, ensuring the wire from solder pad A in Step 4 is connected to terminal block A. Back out the screws if necessary
    8. Tighten the terminal block screws but do NOT yet attach the cover
    9. Remove the plastic pull-tab from the back of the Ecolink sensor to engage the battery
    10. Follow whatever process is required by your Z-Wave controller to detect and include the switch, following the instructions provided with the Ecolink sensor (this may require the switch be in close proximity to the controller)
    11. Once properly detected, replace the cover. Once the cover is closed, the switch shuts down to conserve battery power and will not respond to discovery
    12. If desired, attach the sensor to the top of the receiver with double-sided foam tape (Figure 5)

    At this point a vehicle triggering the receiver should cause a brief transition from Closed to Open status for the switch and can be used to trigger HS4 events as desired. Operation can be tested by pressing the RESET button on the receiver, or passing a shovel or other large metal object over the buried sensor.

    The volume on the receiver can be adjusted as desired without affecting the signal to the switch.

    The sensor switch is normally triggered by proximity to the included magnet. The magnet isn't used in this configuration, but it is important to keep the completed assembly several inches away from any magnets (such as in a speaker) that would lock the switch into a triggered position.

    The Ecolink sensor is powered by a CR123A lithium battery rated to last up to 2 years, depending upon environment and frequency of activation. Battery voltage is monitored and available as a Z-Wave attribute to allow for alerting when replacement time comes.

    The Mighty Mule transmitter is powered by two AA alkaline or lithium batteries. When those are low, the "LOW BAT" LED on the receiver will illuminate, so a periodic check of the LED is necessary. The instructions state that the alarm will beep every 15 seconds when the battery is low, which might trigger the Ecolink sensor. However, in testing with a pair of low batteries, the LED illuminated but no periodic alarm sounded. Your mileage may vary, and requiring some minimum time between alerts in order to trigger a status change may be prudent.

    Opening the cover on the Ecolink sensor activates a tamper warning that requires manual reset, as indicated by the red icon in Figure 6. This can simply be ignored, but if it is bothersome, follow this procedure to reset:
    1. Navigate to the HS4 Status/Graphics page for the sensor and expand the Home Security area
    2. Under Advanced Information, determine the ID for the Home Security property, which will vary depending upon the number of Z-Wave devices present (140 as shown in Figure 7)
    3. Enter the URL below in a browser, substituting the IP of your HS4 system for x.x.x.x and the ID value obtained above for 140, and changing the port to the value for your system if it isn't set to 8080
    4. You should see the message "Response":"ok" as illustrated in Figure 8
    5. Once reset, the tamper indicator changes to green (Figure 9)

    Enjoy, I hope this hack works as well for you as it has for me.

    Photos didn't come through properly on first post.


      Good job.


        I have the same product! Actually, I have 2 of them, since there are two driveway entrances to my house.

        I soldered to the LED leads that light when a vehicle is detected. I ran those to an Arduino that polls every .5 seconds and if the voltage is above 1.2 volts, then the LED is on.
        The Arduino closes a relay which triggers a zone on my OMNI alarm panel and I announce "Vehicle detected in driveway".
        I also do some clever outdoor lighting if a vehicle is detected if the alarm is armed, or it is late at night.
        I then power cycle the receivers with a Z-Wave module to reset the LED.

        Your approach looks great!
        HS4Pro on a Raspberry Pi4
        54 Z-Wave Nodes / 21 Zigbee Devices / 108 Events / 767 Devices
        Plugins: Z-Wave / Zigbee Plus / EasyTrigger / AK Weather / OMNI

        HSTouch Clients: 1 Android


          I looked at the LED as an initial solution but realized the receiver would require a reset and considered using a relay to close the RESET button contacts. The power cycle is a great solution. I also have events that fire when armed or at night, and send a trigger command to a Blue Iris server to mark the camera recording in case motion wasn't detected.

          I've suggested to Mighty Mule the addition of some type of AUX jack or contacts to the unit to allow interfacing with home automation systems, maybe they'll come out with an updated model someday.


            In the Mighty Mule the output of Pin 1 of the PIC (which is indicated as B in the picture above) is a 0-5V digital output to drive the piezo buzzer. It oscillates at about 50Hz. The reset tone is about 235ms long and the regular vehicle detected tone is close to 2 sec.

            I don't have the Ecolink sensor but I assume it is similar to the Honeywell 5816 that I interfaced to the Mighty Mule receiver. The 5816 external loop input is a 0-3V digital input. One terminal is Gnd and the other is the input to the sensor chip through a 100K series resistor. For the 5816 you need to do a little more than just connect the Mighty Mule Gnd to the sensor input Gnd and the Pic Pin 1 output to the other sensor input terminal because there is not enough capacitance to smooth out the 50Hz signal to a simple On - Off. However the 5816 has an unused set of pads from the chip input side to Gnd right beside the 100K signal resistor so adding a 0.1 uf cap there provides a nice low pass filter to the input and the output from the Might Mule is transformed to a nice On - Off square wave at about 2.5V (5V signal at 50% duty cycle). The 5816 does not respond to a signal change that is <~1sec so it does not respond to the reset chirp and will only respond to an actual vehicle notification. But it works for the actual vehicle notifications.

            I'm not sure how the Ecolink sensor works but I assume it is very similar to the 5816 but with a faster response time to a change in input. However unless it has a very fast response time (< 20ms) it must also have some additional capacitance on the input that smoothes the 50Hz Mighty Mule output to trigger the sensor.

            I assume the Ecolink sensor has a significant series resistance on the input to the sensor (like the 5816) in which case it should be safe to feed it a 5V digital signal as there are usually protection diodes to the supply rails to clamp any over/under voltages, plus in this case the signal is a 50% duty cycle signal so with enough resistance and capacitance you end up with ~2.5V anyway. Without scoping the Ecolink sensor it is hard to say how close to the operating margins this “hack” may be.


              clahote I just discovered this excellent post and have purchased both the driveway sensor and the door/window sensor. Your instructions are quite excellent.

              Would it be OK if I reposted this information in a Hubitat forum with a link back to your original posting here? I think some other folks would really like this solution. It's very well thought out and could be used on many different home automation platforms. Excellent problem solving!


                Absolutely, hope it works for you. I've since interfaced the Mightly Mule to a Fortrezz MIMO AC-powered unit to avoid battery changes, but that's a somewhat more expensive solution.


                  Thanks! I'm excited to give it a try.

                  Great point about the battery charge. I wonder if we used a voltage regulator to tap off of the Mighty Mule's power supply, if we could drop the 12V down to the 3V needed for the Ecolink and then not need the battery? Actually, I seem to recall that as soon as the Ecolink's battery has been removed for 10 seconds, it needs to be rediscovered, so that's probably not a viable option.

                  Anyway, thanks, again, can't wait to gave some fun!