Help with setting my "Automated bells" project

Posted by: @alp

What I would like to build is an automated bell. I mean a physical, metal bell that rings every hour. I was thinking I can attach a mini vibration motor to the string of a bell and if I can make the motor turn on every hour, it would shake the bell. Other options are getting a dc motor which will strike the bell instead of shaking it. 

You don't provide complete information, in particular what type of bell, how big the bell and how is it rung now?  Is it like a hand held bell because you talk about giving it a shake? And you talk also about striking the bell.

An Arduino starter kit might cost more than a single Arduino board because it will come with other things like a bread board and various sensors you may not need for a particular project.  These kits are for those who want to learn electronics and programming using an Arduino.

You will need an electronic clock to start with. 

https://dronebotworkshop.com/real-time-clock-arduino/

Thank you for the reply @robotbuilder

I am sorry if I did not give specific details. I assumed I would need the same components in general. Let me try one more time by giving more details. Let's say I want to create a mechanism which will quickly hit a small meditation bowl (the size of a classic British tea cup) on its side to get a nice ring. I am trying to mimic how a person would hit the meditation bowl. I guess I would use a mini linear actuator solenoid which will hit the bell fast and pull back in again. The part that is the most tricky for me is that I would like the bowl to ring randomly every hour. What I mean, it will not ring exactly on every 60 minutes but it will randomise the gaps between the hits ranging from 60 mins to 120 mins. So it might wait 75 mins, or 90 mins, or 110 mins for the next hit (randomly picked by the mechanism). Would it be more simple mechanically if it rings every 60 mins without randomising? 

I am sorry if my English is not clear. Please let me know if this is a good enough description. I am also attaching a picture I made. I would appreciate it if you can let me know how I can make such mechanism and what parts I would need. Thank you again.

Hi @alp,

    @robotbuilder has already provided some good advice.

    I note you have added some information whilst I was writing this, but I think it is still generally appropriate, and hope it is helpful.

As a supplement to this advice, I suggest you also look at the 'bell' end of the project. If you have a particular 'electro-mechanical' solution in mind, then consider prototyping it as a 'sub-project', possibly before worrying about the clock/control mechanism.

Others may be able to offer some suggestions as to how to construct such a bell, but for simplicity (and my lack of mechanical imagination/know how) I am going to imagine you will end up with a 'magic box' with two wires coming out of it. Then, when you apply a suitable power source, to the two wires, the 'magic box' will ring as required.

At this point, you can test your 'magic box' by momentarily connecting to a  battery or other power source you have at hand, which offers the required voltage at sufficient power level.

When you have such a device, you will be in position to specify the voltage and measure the current required to 'activate' your 'magic box' ... then:

• you will have the information needed to design the interface between the clock/control electronics and the 'magic box' (There are people on this forum who can help given the specification information.)
• you will have ensured your 'magic box' is capable of producing the sound you require in appropriate and sufficient volume, etc. - if it is too quiet, it will be missed ... too loud and it might be mistaken for a fire alarm or similar!

As someone who finds electronics easier than mechanics, I would also mention that it may be possible to buy the 'magic box' ... either as a traditional buzzer/bell or maybe based on a power amplifier/speaker which is driven by an appropriate source.

Good luck with your venture! Dave

Thank you @davee for the reply

I made a more detailed description of what I am trying to build above. I want to make a mechanism which will hit a meditation bowl just like a human would do. I also made a picture hoping it would help explaining better. Since I am super new to this, I do not know what I would need to make the  linear actuator solenoid hit the bowl. I would be interest in hearing how you would approach this. Thank you.

@alp 

You might consider using an inexpensive servo with your Arduino. Drill out the last hole in the servo arm and add a bolt with a couple of washers and a nut on it so that the washers protrude past the edge of the servo arm.

Place the servo beside the bell (probably near the top would be best) arranged so that the washers will strike the bell near the end of the arm's rotation.

Then use the Arduino to swing the arm towards the bell every hour. You may need an RTC (real time clock) to get any precision on the bell timing. Move the servo arm back after the strike to avoid having it damp the chime.

This is just an experiment, I don't know if this arrangement will have enough force to sound the bell loudly or whether the chime will be damped by the arm after the strike, so think of it as a quick, dirty and inexpensive prototype 🙂

Hi @alp,

  I see that @Will has kindly provided a suggestion whilst I have been writing my reply.

I'll send my reply as well, so you have a couple of alternates to consider and try. I have the impression there is some 'magic' about making a bell or gong sound 'right', but no experience! all I can do is recommend doing some experiments.

  A linear solenoid of the type your picture shows normally has the moving part which has two positions :

• 'unpowered' when the position of the rod is determined by an internal spring mechanism
• 'powered', when the magnetic force from the electric current passing through the device overcomes the spring force and moves the rod

In principle, it just requires you to connect the wires to a suitable power source (voltage and current specified by the manufacturer) to cause the moving part to actually move to it.

For your application, obviously it might be helpful if the 'unpowered' position was to the right in your picture, and the rod moved to the left. However, if it mains powered, you may not mind it being powered to keep it away from the bowl. I point this out, since you will need to check this when looking for a solenoid. Unfortunately, the common convention is for the power to pull the rod into the solenoid, which is the converse of this.

You might try turning the solenoid through 180 degrees so that it points away from the bowl, attaching a J shaped rod, with the toe of the J attached to the moving end of the solenoid, the stem of the J parallel to the solenoid, and the top of the J forming the hammer head.

You might also try changing the material of the hammer hear that hits the bowl to alter the sound it makes.

Thus, if you buy a solenoid, simply making and breaking the circuit with a suitable power source, whilst holding the solenoid at the appropriate position to your bowl, (you may need a friend or a clamp) should be enough to see if it will produce the right sound.

A quick Google suggested small 6V solenoids are readily available ... which combined with 4 x 1.5V batteries in a holder, could form the basis of your first prototype trials. If you get a 'good' sound, then obviously you will need a mechanical structure to support it. Then just bring out the two wires to connect to a control/clock mechanism ... the next part of the main project!

Good luck and happy experimenting!

thank you for taking time and helping me @Will and @davee

@alp 

The part that is the most tricky for me is that I would like the bowl to ring randomly every hour. What I mean, it will not ring exactly on every 60 minutes but it will randomise the gaps between the hits ranging from 60 mins to 120 mins. So it might wait 75 mins, or 90 mins, or 110 mins for the next hit (randomly picked by the mechanism). Would it be more simple mechanically if it rings every 60 mins without randomising?

So do you actually have this bowl as pictured?
What is the metal thingy in the picture?  It looks like some kind of spring loaded solenoid.

If you have a spring loaded solenoid then play with that until you get the ring you desire.

You might look around for a cheap electric bell and use the mechanism in that? Just replace the metal "bowl" for the one you are using and let the hammer hit that to see how it works. If it works ok we can think about the electronics to trigger it automatically in the random way you outlined above.

https://en.wikipedia.org/wiki/Electric_bell

@alp FYI @robotBuilder

Sorry, that last line ("curr") should not be there, please delete it