Path: csiph.com!eternal-september.org!feeder.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Don Kuenz Newsgroups: sci.electronics.design Subject: Re: How to increase the volume of a metronome? Date: Sat, 25 Feb 2017 03:43:27 -0000 (UTC) Organization: A noiseless patient Spider Lines: 64 Distribution: world Message-ID: <20170224d@crcomp.net> References: <20170224a@crcomp.net> <20170213e@crcomp.net> <20170222b@crcomp.net> <20170223a@crcomp.net> <20170223b@crcomp.net> <95aa4c69-85b3-404d-b892-ad56875cbaf5@googlegroups.com> <20170224a@crcomp.net> <119f985d-7a7a-45bb-8765-f7265487bcf6@googlegroups.com> Injection-Date: Sat, 25 Feb 2017 03:43:27 -0000 (UTC) Injection-Info: mx02.eternal-september.org; posting-host="4b3c70845353415aea08c748e0bda767"; logging-data="4867"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19y2BH0qinSI1URIy0YjVCZ" Cancel-Lock: sha1:g5jwdIHqpKzFk5RrKYA9nQy7Gfw= Xref: csiph.com sci.electronics.design:449126 rickman wrote: > On 2/24/2017 4:23 PM, tabbypurr@gmail.com wrote: >> On Friday, 24 February 2017 20:46:36 UTC, rickman wrote: >>> On 2/24/2017 3:37 PM, tabbypurr wrote: >> >>>>> I get some 600+mA into the speaker which I would think is >>>>> enough, but you'll have to test it to see. This also solves the power >>>>> consumption issue dropping the current over most of the cycle to what it >>>>> takes to charge the timing cap. >>>>> >>>>> When I was working on radio design we were able to drive a 2 watt >>>>> speaker using just 5 volts. I can't imagine you won't get enough volume >>>>> out of this. If you don't, try increasing the value of C1. That will >>>>> give you a wider pulse. >>>>> >>>>> If Vol1 and Vol2 are supposed to be a volume potentiometer, you will >>>>> find the pulse width changing as you change the volume. Add a series >>>>> resistor in line with C1 to give a consistent pulse width over the >>>>> volume range and reduce the value of C1 to suit. This may reduce the >>>>> volume too much which means you will need a second transistor. This is >>>>> a bit more complex, so come back and I'll show you how to add that. >>>>> >>>>> As others have said, the 2N3904 is not rated for the currents, but they >>>>> are only pulses, so it won't over heat the devices. Still, a 1 amp part >>>>> would be good. No need for a heat sink. >>>> >>>> >>>> A 5.2 ohm woofer on a 9v line: 1A transistor is not enough. >>> >>> A 9 volt line from a 9 volt battery with a 2 ohm output resistance. A 1 >>> amp transistor will drive the speaker from his junk pile just fine. I >>> didn't see where he was going to connect this to a woofer. >> >> IIUC he dropped the idea of a battery and went with a wallwart. Either >> way it has a 100uF cap on the psu rails. 5.2 ohm speaker >> with or without 2ohm supply impedace still gets you over 1A. >> >> Woofer details are in loudspeaker.lib. > > Who changed it to a 5.2 ohm woofer? That sounds like overkill to me. Measured voice coil resistance (Re) is one of the parameters used in loudspeaker.lib. My metronome uses a Realistic Minimus 0.3 Bookshelf Speaker (shown here http://www.ebay.com/itm/272541834843 ). It gives the beat a "warm" timbre. That Realistic speaker displays a measured voice coil resistance of 6.5 ohms. It's closer to the Dayton Audio RS225-8 8" Reference Woofer in loudspeaker.lib than the IB3858 speaker used in my metronome.asc. Vol1 and Vol2 do indeed represent a pot. If anyone knows a better way to do that in spice, please let me know. On another note, the LM386 may obviate the need for a wall wart. Regardless, the transistor ideas that you guys are kicking around pique my interest and will be followed up on. Learning something new every day. Carry on. :0) Thank you, -- Don Kuenz KB7RPU