On Thursday, 22 December 2016 23:34:30 UTC, Bill Bowden wrote:> <tabbypurr> wrote in message > news:538f0c48-6447-4144-b74f-c9d15d526463@googlegroups.com... > > On Thursday, 22 December 2016 01:59:45 UTC, Bill Bowden wrote: > >> <dagmargoodboat@yahoo.com> wrote in message > >> news:008d06f2-d9c8-4c49-b5d5-f5b791bd22a4@googlegroups.com... > >> > On Wednesday, December 21, 2016 at 10:59:24 AM UTC-5, Jim Thompson > >> > wrote: > >> >> Problem is that a coupling capacitor will get charged by base current > >> >> on the positive stroke, but then will discharge slowly via the bias, > >> >> creating a threshold movement. > >> >> > >> >> So a simple transistor stage can't maintain a constant threshold. > >> > > >> > That's right, but AIUI he doesn't need a stable d.c. threshold. > >> > > >> > I think it's for a variation on this: > >> > http://www.bowdenshobbycircuits.info/motor.htm#new > >> > > >> > But I'm guessing, & might be mistaken. > >> > > >> > Cheers, > >> > James Arthur > >> > >> You guessed it. I started out with 5 transistors and then refined it to > >> 3. > >> So, I thought I might get it down to 2 transistors. The original design > >> was > >> in a magazine Nuts and Volts I think and only used 2 transistors hooked > >> up > >> as a SCS. The magnet induced a small voltage in the coil which triggerd > >> the > >> SCS which allowed a large capacitor (220uF or so) to discharge through > >> the > >> coil and push the magnet for 15 milliseconds or so. Problem was, the > >> pulse > >> wasn't square and drooped off as the capacitor ran down. And they used a > >> low > >> resistance coil of 30 ohms which wasn't very efficient. My latest model > >> uses > >> a coil with better dimensions and has a wire resistance of about 150 ohms > >> which only draws 20 milliamps at a 10% duty cycle which is about 2 > >> milliamps > >> plus another milliamp bias current, or maybe 3 milliamps total. Using a > >> couple 'D' alkaline cells, it should run for 16/.003 = 222 days. I was > >> thinking if I wanted to use the SCS idea, I only need 2 transistors but > >> the > >> problem is biasing the thing so it triggers on 300mV at about a 10% duty > >> cycle. 90% of the time it doesn't do anything. It only sees one sine wave > >> cycle of about a 25 millisecond half cycle time. > >> > >> . > > > > So what's wrong with the basic 0.3V detector I posted?> > The base voltage should remain constant at about 400mV as the supply voltage > falls from 3.2 to 2 volts. That's why I used a diode.The penny drops. If enough cents drop, does one start to have cents? NT
Bipolar transistor bias question
Started by ●December 18, 2016
Reply by ●December 22, 20162016-12-22
Reply by ●December 22, 20162016-12-22
On Thursday, December 22, 2016 at 6:34:30 PM UTC-5, Bill Bowden wrote:> <tabbypurr@gmail.com> wrote in message > news:538f0c48-6447-4144-b74f-c9d15d526463@googlegroups.com... > > On Thursday, 22 December 2016 01:59:45 UTC, Bill Bowden wrote: > >> <dagmargoodboat@yahoo.com> wrote in message > >> news:008d06f2-d9c8-4c49-b5d5-f5b791bd22a4@googlegroups.com...> >> > I think it's for a variation on this: > >> > http://www.bowdenshobbycircuits.info/motor.htm#new > >> > > >> > But I'm guessing, & might be mistaken. > >> > > >> > >> You guessed it. I started out with 5 transistors and then refined it to > >> 3. > >> So, I thought I might get it down to 2 transistors. The original design > >> was > >> in a magazine Nuts and Volts I think and only used 2 transistors hooked > >> up > >> as a SCS. The magnet induced a small voltage in the coil which triggerd > >> the > >> SCS which allowed a large capacitor (220uF or so) to discharge through > >> the > >> coil and push the magnet for 15 milliseconds or so. Problem was, the > >> pulse > >> wasn't square and drooped off as the capacitor ran down. And they used a > >> low > >> resistance coil of 30 ohms which wasn't very efficient. My latest model > >> uses > >> a coil with better dimensions and has a wire resistance of about 150 ohms > >> which only draws 20 milliamps at a 10% duty cycle which is about 2 > >> milliamps > >> plus another milliamp bias current, or maybe 3 milliamps total. Using a > >> couple 'D' alkaline cells, it should run for 16/.003 = 222 days. I was > >> thinking if I wanted to use the SCS idea, I only need 2 transistors but > >> the > >> problem is biasing the thing so it triggers on 300mV at about a 10% duty > >> cycle. 90% of the time it doesn't do anything. It only sees one sine wave > >> cycle of about a 25 millisecond half cycle time. > >> > >> . > > > > So what's wrong with the basic 0.3V detector I posted? > > > > > > NT > > The base voltage should remain constant at about 400mV as the supply voltage > falls from 3.2 to 2 volts. That's why I used a diode.. _________+ . | | . R2 R3 | | . | |/ . --R1-+---| Q1 . |>. . | . ___________| 0v Then you could use NT's circuit, but replace R1 with a schottky. That does exactly what you want, temperature-compensated for free. Cheers, James
Reply by ●December 23, 20162016-12-23
<dagmargoodboat@yahoo.com> wrote in message news:d4b18bb5-40fa-4987-8551-21bdc478baee@googlegroups.com...> On Thursday, December 22, 2016 at 6:34:30 PM UTC-5, Bill Bowden wrote: >> <tabbypurr@gmail.com> wrote in message >> news:538f0c48-6447-4144-b74f-c9d15d526463@googlegroups.com... >> > >> > So what's wrong with the basic 0.3V detector I posted? >> > >> > >> > NT >> >> The base voltage should remain constant at about 400mV as the supply >> voltage >> falls from 3.2 to 2 volts. That's why I used a diode. > > . _________+ > . | | > . R2 R3 > | | > . | |/ > . --R1-+---| Q1 > . |>. > . | > . ___________| 0v > > Then you could use NT's circuit, but replace R1 with a schottky. > > That does exactly what you want, temperature-compensated for free. > > Cheers, > JamesYes, that might work R2 is fairly high at 100K or more so the drop on a schottky is only 150mV. If I use 1N4148, the drop is about right at 450mV at room temp.I can get it down to 400mV if R2 is 200K. But it looks ok at 450mV and switches the transistor rail to rail with a 250mV input. It's something to play with But right now I have to get Xmas out of the way and get my relatives something so I can show up at Xmas dinner carrying at least 2 gifts. I'm considering a large box of chocolates, or a Hickory Farm box of sausage and cheese, or a box of egg rolls from an Asian market. Plus a gift card of some value. I sent my grand Niece and Nephew each a 50 dollar bill in a card. I hope the postman doesn't rip it off.
Reply by ●December 24, 20162016-12-24
On Friday, December 23, 2016 at 8:05:37 PM UTC-5, Bill Bowden wrote:> <dagmargoodboat@yahoo.com> wrote in message > news:d4b18bb5-40fa-4987-8551-21bdc478baee@googlegroups.com... > > On Thursday, December 22, 2016 at 6:34:30 PM UTC-5, Bill Bowden wrote: > >> <tabbypurr@gmail.com> wrote in message > >> news:538f0c48-6447-4144-b74f-c9d15d526463@googlegroups.com... > >> > > >> > So what's wrong with the basic 0.3V detector I posted? > >> > > >> > > >> > NT > >> > >> The base voltage should remain constant at about 400mV as the supply > >> voltage > >> falls from 3.2 to 2 volts. That's why I used a diode. > > > > . _________+ > > . | | > > . R2 R3 > > | | > > . | |/ > > . --R1-+---| Q1 > > . |>. > > . | > > . ___________| 0v > > > > Then you could use NT's circuit, but replace R1 with a schottky. > > > > That does exactly what you want, temperature-compensated for free. > > > > Cheers, > > James > > Yes, that might work R2 is fairly high at 100K or more so the drop on a > schottky is only 150mV. If I use 1N4148, the drop is about right at 450mV at > room temp.I can get it down to 400mV if R2 is 200K. But it looks ok at 450mV > and switches the transistor rail to rail with a 250mV input. It's something > to play with.A small-signal schottky will have a higher Vf at low current than that 1n5823 you're thinking of using :-). But yes, you could also use a 'fat' diode (such as a 1n4001) at low current instead of a small-signal schottky, and get a suitably smaller Vf.> But right now I have to get Xmas out of the way and get my > relatives something so I can show up at Xmas dinner carrying at least 2 > gifts. I'm considering a large box of chocolates, or a Hickory Farm box of > sausage and cheese, or a box of egg rolls from an Asian market. Plus a gift > card of some value. I sent my grand Niece and Nephew each a 50 dollar bill > in a card. I hope the postman doesn't rip it off.Don't forget, there's always room for Jello! Cheers, James Arthur
Reply by ●December 24, 20162016-12-24
On Monday, December 19, 2016 at 11:32:30 AM UTC-5, Jim Thompson wrote:> On Sun, 18 Dec 2016 16:41:42 -0800, "billbowden" > <bperryb@bowdenshobbycircuits.info> wrote: > > >I have a switching application where a single bipolar transistor might be > >used. The AC input is about 300mV and the transistor needs about 700 mV to > >switch on. My idea is to construct a voltage divider using a diode which > >will produce about a 600mV drop across the diode and a voltage divider of 2 > >equal resistors to set the transistor base voltage at about 300 mV so the > >transistor will switch on with an additional 300mV. I understand the > >temperature problems, but it seems to be minimal. What am I missing? > > > > > > <http://www.analog-innovations.com/SED/ThresholdAmp_Bowden_SED_2016-12-19.png> > > (Pardon my snarky response last night... I fell asleep watching a > movie on TV and didn't read your post carefully :-)That circuit is a fantasy...> > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 |
Reply by ●December 27, 20162016-12-27
<dagmargoodboat@yahoo.com> wrote in message news:b954d064-5417-4629-9805-6296310ca870@googlegroups.com...> On Friday, December 23, 2016 at 8:05:37 PM UTC-5, Bill Bowden wrote: >> <dagmargoodboat@yahoo.com> wrote in message >> > Then you could use NT's circuit, but replace R1 with a schottky. >> > >> > That does exactly what you want, temperature-compensated for free. >> > >> > Cheers, >> > James >> >> Yes, that might work R2 is fairly high at 100K or more so the drop on a >> schottky is only 150mV. If I use 1N4148, the drop is about right at 450mV >> at >> room temp.I can get it down to 400mV if R2 is 200K. But it looks ok at >> 450mV >> and switches the transistor rail to rail with a 250mV input. It's >> something >> to play with. > > A small-signal schottky will have a higher Vf at low current than that > 1n5823 you're thinking of using :-). > > But yes, you could also use a 'fat' diode (such as a 1n4001) at low > current > instead of a small-signal schottky, and get a suitably smaller Vf. > >> But right now I have to get Xmas out of the way and get my >> relatives something so I can show up at Xmas dinner carrying at least 2 >> gifts. I'm considering a large box of chocolates, or a Hickory Farm box >> of >> sausage and cheese, or a box of egg rolls from an Asian market. Plus a >> gift >> card of some value. I sent my grand Niece and Nephew each a 50 dollar >> bill >> in a card. I hope the postman doesn't rip it off. > > Don't forget, there's always room for Jello! > > Cheers, > James ArthurI think I have a working modle using just two transistors. The pulse shape is not the best, but better than the original magazine circuit. .Total part count is 10 verses 12 with the old circuit so I saved 2 parts. And it triggers on 250mV. Haven't built it yet, I'll wait until I sell one of the old ones at Doc's. I sold my original for $25 a couple weeks ago. I think I've sold 6 for around $20 each, so I'm ahead $120 in a couple years. Version 4 SHEET 1 992 680 WIRE 176 -48 80 -48 WIRE 288 -48 176 -48 WIRE 464 -48 288 -48 WIRE 544 -48 464 -48 WIRE 544 -16 544 -48 WIRE -64 0 -208 0 WIRE -16 0 -64 0 WIRE 464 0 464 -48 WIRE 80 16 80 -48 WIRE -208 32 -208 0 WIRE 176 48 176 32 WIRE 208 48 176 48 WIRE 288 48 288 32 WIRE 288 48 272 48 WIRE 304 48 288 48 WIRE 400 48 384 48 WIRE -64 96 -64 64 WIRE -16 96 -16 80 WIRE -16 96 -64 96 WIRE 176 96 176 48 WIRE -16 144 -16 96 WIRE -16 144 -32 144 WIRE 0 144 -16 144 WIRE 80 144 80 96 WIRE 80 144 64 144 WIRE 112 144 80 144 WIRE -176 192 -176 144 WIRE -16 240 -16 144 WIRE 464 240 464 96 WIRE 464 240 -16 240 FLAG 544 64 0 FLAG 176 192 0 FLAG -176 272 0 FLAG -208 32 0 SYMBOL pnp 400 96 M180 WINDOW 3 -24 -21 Left 0 WINDOW 0 -264 -273 Left 0 SYMATTR Value 2N3906 SYMATTR InstName Q1 SYMBOL npn 112 96 R0 WINDOW 0 324 -47 Left 0 WINDOW 3 35 47 Left 0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL voltage 544 -32 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 3.2 SYMBOL diode 64 128 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D1 SYMATTR Value 1N4148 SYMBOL voltage -176 176 R0 WINDOW 3 53 98 Left 0 WINDOW 123 0 0 Left 0 WINDOW 39 57 124 Left 0 WINDOW 0 -73 49 Left 0 SYMATTR Value PULSE(0 4.5 0 1e-6 1e-6 .001 .3 5) SYMATTR SpiceLine Rser=0 SYMATTR InstName V2 SYMBOL res 160 -64 R0 WINDOW 0 -63 435 Left 0 WINDOW 3 37 57 Left 0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL cap 272 32 R90 WINDOW 0 -99 47 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 4.7� SYMBOL res 64 0 R0 WINDOW 0 154 371 Left 0 WINDOW 3 39 50 Left 0 SYMATTR InstName R3 SYMATTR Value 220k SYMBOL res -16 128 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R4 SYMATTR Value 1000k SYMBOL cap -112 128 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C2 SYMATTR Value .1� SYMBOL res 272 -64 R0 WINDOW 0 -256 433 Left 0 WINDOW 3 38 55 Left 0 SYMATTR InstName R5 SYMATTR Value 10k SYMBOL ind -32 -16 R0 WINDOW 0 216 386 Left 0 WINDOW 3 41 49 Left 0 SYMATTR InstName L1 SYMATTR Value .3 SYMATTR SpiceLine Rser=300 SYMBOL diode -80 0 R0 WINDOW 3 -90 38 Left 0 WINDOW 0 331 372 Left 0 SYMATTR Value 1N4148 SYMATTR InstName D2 SYMBOL res 400 32 R90 WINDOW 0 352 328 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 2k TEXT -120 328 Left 0 !.tran 2s
Reply by ●December 28, 20162016-12-28
On Tuesday, December 27, 2016 at 9:02:21 PM UTC-5, Bill Bowden wrote:> <dagmargoodboat@yahoo.com> wrote in message > news:b954d064-5417-4629-9805-6296310ca870@googlegroups.com... > > On Friday, December 23, 2016 at 8:05:37 PM UTC-5, Bill Bowden wrote: > >> <dagmargoodboat@yahoo.com> wrote in message > >> > Then you could use NT's circuit, but replace R1 with a schottky. > >> > > >> > That does exactly what you want, temperature-compensated for free. > >> > > >> > Cheers, > >> > James > >> > >> Yes, that might work R2 is fairly high at 100K or more so the drop on a > >> schottky is only 150mV. If I use 1N4148, the drop is about right at 450mV > >> at > >> room temp.I can get it down to 400mV if R2 is 200K. But it looks ok at > >> 450mV > >> and switches the transistor rail to rail with a 250mV input. It's > >> something > >> to play with. > > > > A small-signal schottky will have a higher Vf at low current than that > > 1n5823 you're thinking of using :-). > > > > But yes, you could also use a 'fat' diode (such as a 1n4001) at low > > current > > instead of a small-signal schottky, and get a suitably smaller Vf. > > > >> But right now I have to get Xmas out of the way and get my > >> relatives something so I can show up at Xmas dinner carrying at least 2 > >> gifts. I'm considering a large box of chocolates, or a Hickory Farm box > >> of > >> sausage and cheese, or a box of egg rolls from an Asian market. Plus a > >> gift > >> card of some value. I sent my grand Niece and Nephew each a 50 dollar > >> bill > >> in a card. I hope the postman doesn't rip it off. > > > > Don't forget, there's always room for Jello! > > > > Cheers, > > James Arthur > > I think I have a working modle using just two transistors. The pulse shape > is not the best, but better than the original magazine circuit. .Total part > count is 10 verses 12 with the old circuit so I saved 2 parts. And it > triggers on 250mV. Haven't built it yet, I'll wait until I sell one of the > old ones at Doc's. I sold my original for $25 a couple weeks ago. I think > I've sold 6 for around $20 each, so I'm ahead $120 in a couple years.<snip LTSpice> That's cute. And power consumption is down below 1mA. Is your coil really 300mH? A nice feature is how easily you can set the output pulse width to minimize power usage. For your amusement, here's a version of your circuit with a MOSFET output. (I injected the simulated coil pick-up voltage slightly differently.) Cheers, James Arthur Version 4 SHEET 1 992 680 WIRE 176 -80 80 -80 WIRE 288 -80 176 -80 WIRE 400 -80 288 -80 WIRE 480 -80 400 -80 WIRE 480 -64 480 -80 WIRE 176 -48 176 -80 WIRE 288 -48 288 -80 WIRE -64 0 -208 0 WIRE -16 0 -64 0 WIRE 80 16 80 -80 WIRE 480 32 480 16 WIRE 400 48 400 -80 WIRE 176 64 176 32 WIRE 208 64 176 64 WIRE 288 64 288 32 WIRE 288 64 272 64 WIRE 352 64 288 64 WIRE -208 80 -208 0 WIRE -64 96 -64 64 WIRE -16 96 -16 80 WIRE -16 96 -64 96 WIRE 176 96 176 64 WIRE -16 144 -16 96 WIRE 0 144 -16 144 WIRE 80 144 80 96 WIRE 80 144 64 144 WIRE 112 144 80 144 WIRE -208 192 -208 160 WIRE 176 208 176 192 WIRE -16 256 -16 144 WIRE 400 256 400 144 WIRE 400 256 -16 256 FLAG 480 32 0 FLAG 176 208 0 FLAG -208 192 0 SYMBOL npn 112 96 R0 WINDOW 0 79 44 Left 2 WINDOW 3 60 73 Left 2 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL voltage 480 -80 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value 3 SYMBOL diode 64 128 R90 WINDOW 0 56 32 VBottom 2 WINDOW 3 54 29 VTop 2 SYMATTR InstName D1 SYMATTR Value 1N4148 SYMBOL voltage -208 64 R0 WINDOW 3 -108 162 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 -112 76 Left 2 WINDOW 0 -73 49 Left 2 SYMATTR Value PULSE(0 300mV 0 1e-6 1e-6 .001 .3) SYMATTR SpiceLine Rser=0 SYMATTR InstName V2 SYMBOL res 160 -64 R0 WINDOW 0 43 32 Left 2 WINDOW 3 37 57 Left 2 SYMATTR InstName R2 SYMATTR Value 22k SYMBOL cap 272 48 R90 WINDOW 0 58 33 VBottom 2 WINDOW 3 56 27 VTop 2 SYMATTR InstName C1 SYMATTR Value 1µF SYMBOL res 64 0 R0 WINDOW 0 46 23 Left 2 WINDOW 3 39 50 Left 2 SYMATTR InstName R3 SYMATTR Value 220k SYMBOL res 272 -64 R0 WINDOW 0 41 29 Left 2 WINDOW 3 38 55 Left 2 SYMATTR InstName R5 SYMATTR Value 22k SYMBOL ind -32 -16 R0 WINDOW 0 38 18 Left 2 WINDOW 3 41 49 Left 2 SYMATTR InstName L1 SYMATTR Value .3 SYMATTR SpiceLine Rser=300 Cpar=300pF SYMBOL diode -80 0 R0 WINDOW 3 -90 38 Left 2 WINDOW 0 -61 13 Left 2 SYMATTR Value 1N4148 SYMATTR InstName D2 SYMBOL pmos 352 144 M180 SYMATTR InstName M1 SYMATTR Value Si1555DL_P TEXT 440 160 Left 2 !.tran 2s TEXT -240 -112 Left 2 ;Bill Bowden's pendulum driver, with MOSFET output 28-Dec-2016
Reply by ●December 28, 20162016-12-28
On 12/27/2016 8:02 PM, billbowden wrote:> <dagmargoodboat@yahoo.com> wrote in message > news:b954d064-5417-4629-9805-6296310ca870@googlegroups.com... >> On Friday, December 23, 2016 at 8:05:37 PM UTC-5, Bill Bowden wrote: >>> <dagmargoodboat@yahoo.com> wrote in message >>>> Then you could use NT's circuit, but replace R1 with a schottky. >>>> >>>> That does exactly what you want, temperature-compensated for free. >>>> >>>> Cheers, >>>> James >>> >>> Yes, that might work R2 is fairly high at 100K or more so the drop on a >>> schottky is only 150mV. If I use 1N4148, the drop is about right at 450mV >>> at >>> room temp.I can get it down to 400mV if R2 is 200K. But it looks ok at >>> 450mV >>> and switches the transistor rail to rail with a 250mV input. It's >>> something >>> to play with. >> >> A small-signal schottky will have a higher Vf at low current than that >> 1n5823 you're thinking of using :-). >> >> But yes, you could also use a 'fat' diode (such as a 1n4001) at low >> current >> instead of a small-signal schottky, and get a suitably smaller Vf. >> >>> But right now I have to get Xmas out of the way and get my >>> relatives something so I can show up at Xmas dinner carrying at least 2 >>> gifts. I'm considering a large box of chocolates, or a Hickory Farm box >>> of >>> sausage and cheese, or a box of egg rolls from an Asian market. Plus a >>> gift >>> card of some value. I sent my grand Niece and Nephew each a 50 dollar >>> bill >>> in a card. I hope the postman doesn't rip it off. >> >> Don't forget, there's always room for Jello! >> >> Cheers, >> James Arthur > > I think I have a working modle using just two transistors. The pulse shape > is not the best, but better than the original magazine circuit. .Total part > count is 10 verses 12 with the old circuit so I saved 2 parts. And it > triggers on 250mV. Haven't built it yet, I'll wait until I sell one of the > old ones at Doc's. I sold my original for $25 a couple weeks ago. I think > I've sold 6 for around $20 each, so I'm ahead $120 in a couple years.Well, your OP indicated you wanted to use one transistor and that the input voltage would be 300mV. So, the specs have changed now? Where can I find the 250mV trigger in the simulation? (Snip LTSpice listing)
Reply by ●December 28, 20162016-12-28
"John S" <Sophi.2@invalid.org> wrote in message news:o4142f$d56$2@dont-email.me...> On 12/27/2016 8:02 PM, billbowden wrote: >> I think I have a working modle using just two transistors. The pulse >> shape >> is not the best, but better than the original magazine circuit. .Total >> part >> count is 10 verses 12 with the old circuit so I saved 2 parts. And it >> triggers on 250mV. Haven't built it yet, I'll wait until I sell one of >> the >> old ones at Doc's. I sold my original for $25 a couple weeks ago. I think >> I've sold 6 for around $20 each, so I'm ahead $120 in a couple years. > > Well, your OP indicated you wanted to use one transistor and that the > input voltage would be 300mV. So, the specs have changed now? > > Where can I find the 250mV trigger in the simulation? > > (Snip LTSpice listing) >The OP just concerned switching the first transistor.I didn't care much about the second. The way I tested for 250mV was to disconnect the 4.7u capacitor and apply a 250mV sine at 20 hertz directly to the cathode of the diode, Then look at the collector of the 3904 and it will swing almost rail to rail (3.2 to .0.15)
Reply by ●December 28, 20162016-12-28
On 12/28/2016 3:50 PM, billbowden wrote:> "John S" <Sophi.2@invalid.org> wrote in message > news:o4142f$d56$2@dont-email.me... >> On 12/27/2016 8:02 PM, billbowden wrote: >>> I think I have a working modle using just two transistors. The pulse >>> shape >>> is not the best, but better than the original magazine circuit. .Total >>> part >>> count is 10 verses 12 with the old circuit so I saved 2 parts. And it >>> triggers on 250mV. Haven't built it yet, I'll wait until I sell one of >>> the >>> old ones at Doc's. I sold my original for $25 a couple weeks ago. I think >>> I've sold 6 for around $20 each, so I'm ahead $120 in a couple years. >> >> Well, your OP indicated you wanted to use one transistor and that the >> input voltage would be 300mV. So, the specs have changed now? >> >> Where can I find the 250mV trigger in the simulation? >> >> (Snip LTSpice listing) >> > > The OP just concerned switching the first transistor.I didn't care much > about the second. The way I tested for 250mV was to disconnect the 4.7u > capacitor and apply a 250mV sine at 20 hertz directly to the cathode of the > diode, Then look at the collector of the 3904 and it will swing almost rail > to rail (3.2 to .0.15)This has become completely ridiculous.
