Introduction: Automatic Church Bell Ringer
I set up a system to automatically ring a church bell. The bell in question sits about 75 ft above street level in a church bell tower. It's about 40 inches in diameter at the base. It was cast in 1896 at the McShane Bell Foundry in Baltimore.
This Instructable shows how I made a working prototype.
My primary goal is I want it to ring on the hour, every hour, between 9:00am and 6:00pm.
I'm using an Uno, RTC DS3231, and a relay. These control the solenoid, which drives the hammer, which strikes the bell.
Working video of the bell ringing is at the end of the Instructable.
Adafruit RTC DS3231
Step 1: Set Up the Solenoid and Hammer
I wanted to build all this on the workbench so I could test it out BEFORE I started climbing any ladders.
But before I start, what kind of solenoid am I using? I am using a 20 pound pull solenoid. (By the end, you'll see I decide to go with TWO solenoids.) These solenoids are normally used in a commercial laundry washing machine or dryer to keep the door locked. Or they are often used to open/close dampers for boilers systems.
The solenoid(s) are what will drive the hammer to strike the bell.
So first step, I needed to attach a hinge on the bottom of a 4 lb hammer.
I had to clean off the handle and put a straight edge on it, parallel to the face of the hammer. This is easy to do on a table saw.
Pretty straight forward. I used a 3 inch hinge to attach the hammer to my base.
(Note: I actually did have to climb the ladder to the bell tower several times at this point. I did lots of measuring and photo taking, and remeasuring. This was important. I wanted the unit to FIT under the bell properly. It would be horrible if I did this work and it didn't fit!)
Step 2: Linkage
So I needed to link the solenoid to the hammer now. And I needed the solenoid (and linkage) to
1) Clear the motion of the hammer, and
2) I needed it to sit away from the edge of the bell.
So I measured and placed it about 8 inches away from the hammer and at least 3 inches below the edge of the bell.
I used a 4 inch hinge to attache the linkage to the hammer.
And yes, my workbench is THAT messy. I'm not proud of it. Just full disclosure. (Mental note for future: Photos for Instructables come out nicer when work bench isn't messy!)
(What's not pictured here is I came back and decided to install 2 solenoids, link them together with some threaded rod, and wire them in parallel.)
Step 3: Arudino
I know the board looks a mess. It is. Remember this is my prototype. I will build or 3D print an enclosure for the board and the RTC. I will put the relay in grounded box and run it to the top of the bell tower with BX conduit (exterior grade) and ground it all and put a 15 amp fuse on the circuit. I obviously don't want to burn the church down if something goes wrong.)
I'm not a master coder. I know this could be cleaned up and made more efficient (e.g. I don't really need the for next loop to read the "strike hours" set up in the array.) Code is attached.
Step 4: Exterior
I may go back and weld a frame instead of using wood. Or paint the wood or use treated...not sure yet.
I also will need to build exterior grade enclosures. While the equipment will be protected from any rain or snow falling when there is NO wind, if there IS wind the moisture will certainly find it's way to the equipment, solenoids, etc.
The Arduino will be inside about 6 feet away, protected inside the church, so no worries there.
Step 5: Working Prototype
Here's a short video of the working system with three merged clips.
Clip 1) The sound of the bell from the street level heard/videoed by my helper (and her dog who doesn't like the bell).
Clip 2) Test of the solenoids/hammer by simply engaging them in the bell tower (I am wearing earplugs!).
Clip 3) First test of the system hooked up to the Arduiino, RTC, and relay at 5:00pm.
Step 6: Improvements
Now that I know it works, I'm debating to add another solenoid or a heaver hammer. Or tilting the bell a few degrees to make better contact. Or filing the hammer down so it hits "squarely" on the bell for full contact. Not sure yet but I want to make some adjustments. The "volume" is acceptable, but I want it a bit louder.
The relay is set to engage for 100ms and then there is a 2000ms delay. I'll play around with these settings.
Thanks for viewing. If you end up building something like this or have any ideas for improvement, please share in the comments!