Ringing a magneto phone bell with a motor driver, but volume too low

The two windings are always in series.

To connect them in parallel, unsolder the middle connection between the two. Connect each of the terminals you have unsoldered to the outside connection on the opposite winding. The phase will be correct.

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Hi,

At 18V, the setup pulls 134mA when idle and 145mA when ringing.
At 20V, it pulls 122mA when idle and 122mA when ringing (except it doesn't).

Why does it pull current when idle.
Please define idle.

What is the total DC resistance of the coils?
What current is your lab supply rated at?
You have got the current limit turned up?

What are you doing with the EN pin of the 298?
Connect it to 5V, rather than leave it open circuit.

Can you please post a picture(s) of your project?

Thanks.. Tom... :smiley: :+1: :coffee: :australia:

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It rings! (louder!)

That’s it! I had it all backward. the nano was powered by the +5 from the driver, and the ln298 logic was powered from the however many volts I was ramping it up with. Now, nano has power from usb and ln298 logic has power from the nano’s +5V. And I can ramp up the power suply to max 31V to hear beautiful music, no problem! Yup, the EN pin is now connected to 5V :slight_smile:

Of course I still have a need to run it on battery, though. Perhaps I still need to go in the direction of @SteveMann ‘s transformer circuit? or a boost converter?

yes, I can:


And when it was still wholesome(ish):

Wonderful people, thank you!

There's two windings on a common core. You will have to experiment with the wiring to get the maximum effect.

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@didg good to see you got it working!

Are you on Facebook? You might be interested in

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A boost converter is a fraction of the cost of a transformer (new prices) . You've mentioned my ringer circuit in post #1 Ringer circuit for vintage telephone bells.. You can strip this down to the basics but using your L298. I did some fancy things like emulating the GPO standard ring tone etc. and efforts to minimise power consumption by shutting everything off. I did intent to trigger a ring burst using a PIR sensor but that part of the project still has status "pending".

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Well, that diagram does not help at all. :astonished: It is absolutely not a matter of experimentation.

I was careful to explain that if re-wiring for parallel, the original connections from the ringer circuit to the ends of the coils always remain in place. The connection between the coils is separated, and the connection of each of these goes to the outer end of the other. That way the phasing is not changed.

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Ah, that was yours! I thought that looked like and elegant solution. Then I will order, and try with a boost converter.

I'll start looking into power saving modes too, like you did. I'm planning to trigger the ringing with an NRF24L01 - hopefully that doesn't exclude a power saving mode. (I'll take a deeper dive into the files you put in your post)

@6v6gt What are you using your bell for?

@PerryBebbington Thanks, I'll check out the facebook group!

@Paul_B Could rewiring for parallell further enhance the ringing?

The next step of this project is to shut off ringing and trigger sound files to be played through the handset when lifted off the hook. The earpiece is still functional (connected with and audio jack) and has a great "crackling" sound to it :slight_smile:

Do you mean it naturally crackles? Usually caused by carbon granule transmitters (microphones) when they get old.

Wrong word I suppose. "Distance" would be better, not sure what would best describe it. In the future, I'd love to try to get the carbon granule microphone working too! When I first opened it, I had no idea what all that black "dust" that fell out was :flushed: , but I managed to get it safely back in it's container again.

That 'black dust' is kind of essential to the working of the microphone! It is a crude variable resistor. Something that might be of interest is that carbon granule microphones have gain, as in the act like there is an amplifier in there. They are also very, very low fidelity; if you have an oscilloscope compare the output of a carbon granule microphone to the output of any other kind.

"The outer end of the other"?
Since the coil ends aren't labeled, experimenting is the only way to determine the correct wiring. If out of phase, one coil will null the other since they are on a common core.

The carbon grains absorb water vapor and clump together. I grew up in Houston where the relative humidity is 99% and we would occasionally bang the handset on the desktop to be heard better.

Despite working in telecoms and changing many carbon granule transmitters I never found out the real reason they degraded. I always put it down to it being such a crude technology. They were not just unreliable in Houston, they were unreliable in the UK just as much. Banging them fixed them for a short time, the only real fix was a new one.

Do let us know which way you go with the ringer circuit. There seems to be several options and I am going to re-do my Escape Room Telephone soon. I am breaking so many Arduino rules with my current version that I am surprised that it's still working. (But it was one of my first Arduino projects.)

I, too, worked in telecoms (BT, 1973 to 2005). I was told that voltage spikes on the line was one cause of the clumping. The trimphone - which had a different, and much smaller carbon microphone (sorry, "transmitter") - was very, very prone to microphone crackle. The official fix was to fit one of those bi-directional voltage clippers across the microphone, thus protecting the microphone from the voltage spikes.

I can't remember now how successful it was - the trimphone was never that popular anyway.

What technology did those voltage clippers use? Back-to-back zeners? Or something else? We used to call them "smarties".

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Yes, I realised that after a bit of reading :slight_smile: All in a safe place now.
I do wish I had an oscilloscope, but I'll have to just enjoy the audible experience when I get that far.

For sure. I'm going to try to add the boost converter to my existing setup first (and simplest for now) and see how that pans out. I'll update with the progress. Do you have two-way communication on yours? What solution have you used for that?

My original intention was to create a sort of presence detector for an outside door. With two PIR detectors it could determine if someone from outside was entering the room, but would be unaffected by activity in the room itself, and then, if detected, sound a standard GPO type ring. British GPO 746 Telephone: Ringing - YouTube so as not to alarm the "intruder" who would simply think the telephone was ringing. The basic circuit works but I still have to design a base unit including batteries, a charging part and the PIR detectors. I could (just) have included all that in the bell box but I did not want to drill more holes in that original box.

Anyway, this is another of my projects which is currently pending the allocation of more resources.

If you do decide to build exactly that project take note of the errata in the body of the description.

No. My next version might, or at least rudimentary voice recognition for "yes", "no" and numbers. On mine, the user dials a phone number and hears a phone ringing (random length, just like real phones), then a recording answers. The recording either has a clue or a hint. Some are just for fun. For example if you dial "popcorn" (are you old enough to remember this?) they hear an ad and the current time. The game controller can send clues or hints to the phone (all prerecorded). The phone rings, and when they pick it up they hear the recording with a clue or hint.

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Nice! Great idea. Subtle, but unmistakable.

Yeah, I had totally forgotten that was actually a service one could dial!

That sounds great! Very clever - I like how you can then choose what is played, depending on the situation. Mine would just be the single file played, but this is giving me ideas :slight_smile: Thanks for sharing!