Quote from: TinselKoala on April 22, 2014, 03:02:28 PM
The Blue trace is the signal to the base of the 2SC1815? The channel is set to 5 V/ Div? So you are applying pulses of about 9V peak to the Base of the transistor?
But... but.....  V_EBO is 5V Max.

Maybe he was measuring on the other side of the base resistor that dropped the voltage.

Quote from: avalon on April 22, 2014, 03:17:44 PM
Hmm.... I don't get it either. The signal amplitude on the base is 2.4V
I have attached a couple of pictures. The first one is on the output of 74HC14AN (pin 6) and the second one is @ the base of C1815.

The power supply is 3.30 v
I have no idea how the error occurred.

~A

That makes a lot more sense. Maybe the scope probe attenuation was misset or something. Thanks for checking.... but now my theory about overdriving the transistor is out the window, I guess. Still, that collector current trace doesn't look right either.

Quote from: avalon on April 22, 2014, 03:17:44 PM
Hmm.... I don't get it either. The signal amplitude on the base is 2.4V
I have attached a couple of pictures. The first one is on the output of 74HC14AN (pin 6) and the second one is @ the base of C1815.

The power supply is 3.30 v
I have no idea how the error occurred.

~A

Avalon,

The signal indicated by your scope at the base of your transistor looks like a square wave with a peak to peak value of 800mv or so.  It also has a DC offset of approx. 200mv above ground when the driver IC output is low.  Looking at your schematic, this is just what would be expected.

Regarding the transistor, the base-emitter junction appears to the outside world as a simple diode.  This "diode" (the base) begins to conduct at around .65volts (relative to the emitter) and will conduct a lot of current, just like a diode.  However, looking at the absolute maximum allowed base to emitter current in the data sheet TK provided, the base-emitter current must be limited so as not to exceed 50ma or the base junction can be damaged.

In the top scope trace, your driver IC is outputting a 3.2 volt or so pk-pk square wave.  The driver IC cannot pull its output all the way to ground, so you have a slight offset above ground indicated of a few hundred millivolts when the output is low.

The voltage between the base and emitter of a silicon bipolar transistor that is turned on will always be one silicon diode voltage drop, or between .6 and .8 volts, depending on how much current is being applied to the base and the temperature of the transistor.  Remember, a bipolar transistor is a current controlled device, not a voltage controlled device like a MOSFET.  The amount of current flowing thru the base-emitter junction is multiplied by the current gain of the transistor and that product of base current times the current gain determines the max current that can flow thru the collector emitter junction.

In your circuit, your driver IC puts 3.2V on the 1K resistor.  The base-emitter voltage is about .7V.  So, (3.2V-.7V)=2.5V, which is the voltage drop across the 1K resistor when the transistor is on.  2.5V/1000R equals 2.5ma of base current.

Regarding your scope.  The numbers in the first box at the lower left are the delta V cursor readout.  Your V cursors are not really set to measure anything in the screenshots you provided.  Using the cursor controls, move the lower horizontal dotted line (the Vref cursor) up to the channel one ground reference, which is the arrow at the left of the screen labeled "1".  Now move the upper V cursor to the top of the channel one square wave and your cursor readout will reflect the the actual voltage being output from your IC (upper screen) or applied to your transistor base (lower screen).

Similarly, you can use the time cursors to measure horizontal features. 

I can't make any sense of the "Vbt" readout, perhaps TK or someone else can enlighten us. 

Also, it looks like the trigger is set for a falling edge on channel one but the trigger level is set higher than the signal on channel one.

TK can be a great help with "scoposcopy" skills.

Regarding the weird collector waveforms, try disconnecting your coil and run a 1K resistor from the 3.3V rail to the transistor collector and then take a look at the collector signal with your scope.  If it remains flaky, your transistor has issues.

PW

Added:  Also, always try to align the channel ground reference markers with a major division on the graticule.  This makes it much easier to measure voltage off the screen by counting division.

Wesley Translate's Akula video #16: Akula's TPU part 5



https://www.youtube.com/watch?v=Lpx1SJdXnmo&feature=youtu.be






Wesley

Не знаю, что было раньше, но теперь поставил новую 34063 микросхему, поставил 560 пикофарад купленый конденсатор и без второй микросхемы потребление 7 милиампер.
I now use new 34063 and put 560 picofarad capasitor and now curent consumption wihout second chip (it disconected) is 7 miliamps from 6 volts. But probarly I somewere made error.
Похоже правильно всё спаял и напряжение поднимает, вход 3 вольта, на конденсаторе 1000 мкф больше, но тот раз было 100-200 милиампер, а теперь 7-20 милиампер где-то или может я попортил и теперь микросхему и она не так работает как надо? Или может тогда было где-то ошибка в плате?..
Seems no errors, all errors i find and fix, maybe 34063 I brake.