Put the speaker in the collector line and you'd get more volume. Digital logic is probably the best option, but not the only one. You could probably make it work without the dc by having both npn & pnp trs with CR on their bases. Either transition causes one to pass a single shot of speaker current. You could probably implement the whole lot with a hex buffer plus an output transistor, no 555.
At 200mA max, 2N3904 is way underrated. You'd need a 2A transistor at least.
NT
I'm not sure all the comments about this circuit are important. Adding a cap and diode to the base drive turns the positive edge into a sharp pulse. 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.
-- Rick C
On 2/24/2017 2:11 PM, rickman wrote:
Version 4 SHEET 1 960 936 WIRE -384 96 -512 96 WIRE -288 96 -384 96 WIRE 64 96 -288 96 WIRE 112 96 64 96 WIRE 496 96 112 96 WIRE 112 112 112 96 WIRE -384 128 -384 96 WIRE -288 192 -288 96 WIRE -240 192 -288 192 WIRE 112 192 112 176 WIRE 112 192 -16 192 WIRE 112 224 112 192 WIRE -384 256 -384 208 WIRE -240 256 -384 256 WIRE 16 256 -16 256 WIRE -384 304 -384 256 WIRE -240 320 -320 320 WIRE 176 320 -16 320 WIRE 176 336 176 320 WIRE -240 384 -288 384 WIRE 64 384 64 96 WIRE 64 384 -16 384 WIRE 496 400 496 96 WIRE -384 448 -384 384 WIRE -320 448 -320 320 WIRE -320 448 -384 448 WIRE 16 448 16 256 WIRE 16 448 -320 448 WIRE 176 448 176 416 WIRE 240 448 176 448 WIRE 272 448 240 448 WIRE 368 448 336 448 WIRE 432 448 368 448 WIRE -512 464 -512 96 WIRE -384 464 -384 448 WIRE -288 464 -288 384 WIRE 176 496 176 448 WIRE 496 512 496 496 WIRE 368 528 368 448 WIRE 496 528 496 512 WIRE -512 592 -512 544 WIRE -384 592 -384 528 WIRE -384 592 -512 592 WIRE -288 592 -288 528 WIRE -288 592 -384 592 WIRE 176 624 176 576 WIRE 368 624 368 592 WIRE 496 624 496 608 WIRE -512 640 -512 592 FLAG -512 640 0 FLAG 112 224 0 FLAG 176 624 0 FLAG 496 624 0 FLAG 368 448 Base FLAG 240 448 Cap FLAG 496 512 Spkr FLAG 368 624 0 SYMBOL Misc\\NE555 -128 288 M0 SYMATTR InstName U1 SYMBOL res -368 112 M0 SYMATTR InstName Tempo1 SYMATTR Value 125k SYMBOL res -368 288 M0 WINDOW 0 36 43 Left 2 WINDOW 3 49 74 Left 2 SYMATTR InstName Tempo2 SYMATTR Value 125k SYMBOL cap -368 464 M0 WINDOW 0 -23 6 Left 2 WINDOW 3 -41 58 Left 2 SYMATTR InstName C2
SYMBOL res 160 320 R0 WINDOW 0 -59 39 Left 2 WINDOW 3 -58 71 Left 2 SYMATTR InstName Vol1 SYMATTR Value 5 SYMBOL Misc\\battery -512 448 R0 WINDOW 0 11 6 Left 2 WINDOW 3 5 126 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 5 98 Left 2 SYMATTR InstName V1 SYMATTR Value PULSE(0 9 0 0.001) SYMATTR SpiceLine Rser=2 SYMBOL cap -304 464 R0 SYMATTR InstName C3 SYMATTR Value 0.1nF SYMBOL cap 96 112 R0 SYMATTR InstName C4
SYMBOL res 160 480 R0 WINDOW 0 -57 41 Left 2 WINDOW 3 -59 68 Left 2 SYMATTR InstName Vol2 SYMATTR Value 995 SYMBOL npn 432 400 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 480 512 R0 SYMATTR InstName Speaker SYMATTR Value 8 SYMBOL cap 272 464 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C1
SYMBOL schottky 384 592 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D1 SYMATTR Value BAT54 SYMATTR Description Diode SYMATTR Type diode TEXT -392 616 Right 2 !.tran 1 uic TEXT -8 176 Left 2 ;1 TEXT -8 240 Left 2 ;2 TEXT -8 304 Left 2 ;3 TEXT -8 360 Left 2 ;4 TEXT -296 368 Left 2 ;5 TEXT -296 304 Left 2 ;6 TEXT -296 240 Left 2 ;7 TEXT -296 176 Left 2 ;8
-- Rick C
But then he'll only hear every other edge. That's fine if the OP doesn't mind losing the ability to hahve different mark/space ratios, but I presumed from his design that wasn't the case.
A 5.2 ohm woofer on a 9v line: 1A transistor is not enough.
NT
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.
-- Rick C
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.
NT
Who changed it to a 5.2 ohm woofer? That sounds like overkill to me. BTW, I reduced the cap to 10 uF. It's just a freakin metronome.
-- Rick C
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
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
You don't need to waste current with a single transistor output, just have the 555 output a short fixed length pulse when it goes high rather than a long variable one. 100uF seems small for battery use.
Compared to AA or AAA, 9v PP3s are low capacity and high price per capacity. I avoid using them when practical.
NT
On 2/24/2017 10:43 PM, Don Kuenz wrote:
I tried something a bit different, a simpler design. Personally, if I were going to do anything more complex than this, I would use an MPU which will give you dead accurate timing and volume independent of battery state, wall wart or anything else plus the sound can be controlled both in volume and tone. But this design only has two transistors and a few passives and should give you a decent sound. The power consumption is very low, 8 mA (average) on the fastest setting (about 5 beats per second) giving a life of well over 60 hours from a 9 volt battery in normal use.
The speaker gets a pulse that is only a few ms wide, but the current is controlled rather than the pulse width. So the sound will remain the same over the full volume. Here is the LTspice file. You will need the files for the 2N2426 component too. Run using the alternate solver.
----nujt.asy---- Version 4 SymbolType CELL LINE Normal 24 16 24 80 LINE Normal 48 72 48 96 LINE Normal 24 72 48 72 LINE Normal 48 24 48 0 LINE Normal 24 24 48 24 LINE Normal 6 44 12 36 LINE Normal 6 44 24 53 LINE Normal 12 36 24 53 LINE Normal 0 32 9 40 LINE Normal -16 32 0 32 WINDOW 0 56 32 Left 0 WINDOW 3 56 72 Left 0 SYMATTR Value UJT SYMATTR Prefix X SYMATTR Description N-Channel Unijunction Transistor, Netlist order E, B1, B2 PIN -16 32 NONE 0 PINATTR PinName E PINATTR SpiceOrder 1 PIN 48 96 NONE 0 PINATTR PinName B1 PINATTR SpiceOrder 2 PIN 48 0 NONE 0 PINATTR PinName B2 PINATTR SpiceOrder 3
----2n2646.sub----
----Metronome_UJT.asc---- Version 4 SHEET 1 1992 3388 WIRE -448 368 -624 368 WIRE -352 368 -448 368 WIRE -288 368 -352 368 WIRE -64 368 -288 368 WIRE -64 400 -64 368 WIRE -288 416 -288 368 WIRE -448 432 -448 368 WIRE -64 528 -64 480 WIRE -624 544 -624 368 WIRE -288 560 -288 496 WIRE -240 560 -288 560 WIRE -288 576 -288 560 WIRE -64 592 -64 528 WIRE -448 608 -448 512 WIRE -384 608 -448 608 WIRE -352 608 -384 608 WIRE -128 640 -160 640 WIRE -448 704 -448 608 WIRE -288 704 -288 672 WIRE -208 704 -288 704 WIRE -160 704 -160 640 WIRE -160 704 -208 704 WIRE -64 736 -64 688 WIRE -288 752 -288 704 WIRE -64 784 -64 736 WIRE -624 896 -624 624 WIRE -448 896 -448 768 WIRE -448 896 -624 896 WIRE -288 896 -288 832 WIRE -288 896 -448 896 WIRE -64 896 -64 864 WIRE -64 896 -288 896 WIRE -624 928 -624 896 FLAG -624 928 0 FLAG -384 608 E1 FLAG -208 704 B1 FLAG -240 560 B2 FLAG -352 368 V9 FLAG -64 528 SPKR FLAG -64 736 VOL SYMBOL voltage -624 528 R0 WINDOW 123 0 0 Left 2 WINDOW 39 24 124 Left 2 SYMATTR SpiceLine Rser=1 SYMATTR InstName V1 SYMATTR Value 9 SYMBOL nujt -336 576 R0 SYMATTR InstName U2 SYMATTR Value X2N2646 SYMATTR Description N-Channel Unijunction Transistor SYMBOL res -304 400 R0 SYMATTR InstName R1 SYMATTR Value 100 SYMBOL res -304 736 R0 SYMATTR InstName R2 SYMATTR Value 100 SYMBOL res -464 416 R0 SYMATTR InstName SPEED SYMATTR Value 25k SYMBOL cap -464 704 R0 SYMATTR InstName C1
SYMBOL npn -128 592 R0 SYMATTR InstName Q1 SYMATTR Value 2SCR512P SYMBOL res -80 384 R0 SYMATTR InstName SPKR SYMATTR Value 5.2 SYMBOL res -80 768 R0 SYMATTR InstName VOL SYMATTR Value 1 TEXT -640 248 Left 2 !.tran 0 2 0 .01m TEXT -640 280 Left 2 !.options plotwinsize=0 TEXT -640 312 Left 2 ;.options trtol=1e-1 TEXT -640 -200 Left 2 ;Unijunction Transistor 2N2646\n \nUse the Alternate-solver.\nControl Panel -> SPICE -> Solver:Alternate\n \nThe discharge slope is too steep at the end and thus a very small\ntime step would be required to improve the simulation accuracy\nof the lower peaks. This is a model issue! TEXT -336 248 Left 2 !.include 2n2646_ltspice.sub TEXT -640 48 Left 2 ;A small modification of the model has been required for LTspice.\n
-- Rick C
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