Thread: Incorrect bell?
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Old 2nd Jun 2019, 1:38 pm   #26
PickleRick63
Retired Dormant Member
 
Join Date: May 2019
Location: London, UK.
Posts: 13
Default Re: Incorrect bell?

Delighted to report back with a semi success story!

I used a very small SMPSU rated primary 100V~ @ 50-60hz and secondary DC 9V as per attached photo. The bell rings, although it struggles a bit! It's not got a great rhythm (which suggests that the circuit doesn't have time to get up to speed each time the ringing current is applied on the primary side as per Julie's earlier advice). But it's a nice volume; I wouldn't want it a lot louder, but I would like it to be more regular...

Measuring the voltage on the secondary side my multi-meter (with the reading struggling to keep up with the ring cycle - quite a slow 'sample rate' on this one I guess) reads no more than ~4V which makes sense... this is in proportion with the 50% drop in frequency, and a further loss in proportion with the expected 70V on the line. So ideally I would find an alternative PSU which is going to A) deliver within the range of 6-12V (which is what the bell I'm using is rated at) and B) 'charge' up quickly so the rhythm is better.

The bell has a resistance of 50 Ohms. So if I'm going to look for a PSU capable of 9V at 0.2A. I might need to put a resistor in line if it's too loud I guess.

But I'm not sure how to ascertain whether the PSU I find will 'charge' quickly enough... I have shortlisted the following components as suitable:

https://uk.rs-online.com/web/p/embed...-smps/1812110/

https://uk.rs-online.com/web/p/embed...-smps/1358918/

They are both rated min 85V AV on the primary side - I don't think that's too much of a problem though is it?

And I can't see any published info on the minimum 'charge' length for the secondary circuit to become active but would expect these devices to be pretty quick... a reasonable assumption, do you think?
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