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university:courses:alm1k:alm-lab-15 [05 Nov 2021 14:55] – [Background Basics:] Doug Merceruniversity:courses:alm1k:alm-lab-15 [30 Dec 2021 19:17] (current) – [Gated Oscillator Integrated Circuit] Doug Mercer
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 <WRAP centeralign>Figure 3, solar garden light circuit</WRAP> <WRAP centeralign>Figure 3, solar garden light circuit</WRAP>
  
-The YX8018 comes in a 4 pin transistor style TO-94 package and the pin configuration and block diagram is shown in figure 4. A low voltage near the negative battery voltage (GND) on the CE input of the YX8018 gates off the oscillator.  A high voltage near the positive battery voltage (V<sub>DD</sub>) conversely gates the oscillator on. Other versions of these LED drivers may work opposite so be sure to check your particular IC confirm how the CE control input operates.+The YX8018 comes in a 4 pin transistor style TO-94 package and the pin configuration and block diagram is shown in figure 4. A low voltage near the negative battery voltage (GND) on the CE input of the YX8018 gates off the oscillator.  A high voltage near the positive battery voltage (V<sub>DD</sub>) conversely gates the oscillator on. Other versions of these LED drivers may work opposite so be sure to check your particular IC to confirm how the CE control input operates.
  
 {{ :university:courses:alm1k:alm-lab15_f4.png?500 |}} {{ :university:courses:alm1k:alm-lab15_f4.png?500 |}}
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 Applying a pulse width modulated square wave using one of the generator output channels from the ALM1000 to drive the CE input could serve as a way to change the brightness of the LED. Applying a pulse width modulated square wave using one of the generator output channels from the ALM1000 to drive the CE input could serve as a way to change the brightness of the LED.
  
-By adding another diode and capacitor negative output voltages can be generated as shown in figure 7. A negative voltage is not necessarily needed to drive the LED. This is more a demonstration of how DC-DC converters can also generate negative voltages from positive voltages. Capacitor C<sub>1</sub> and diode D<sub>1</sub> level shift the positive peaks of the voltage waveform at pin 1 and clamp the voltage seen at the junction of D<sub>1</sub> and D<sub>2</sub> to a diode above ground. This now negative going waveform is rectified by D<sub>2</sub>and filtered by C<sub>2</sub>. Again a more efficient design would be to use Schottky diodes.+By adding another diode and capacitornegative output voltages can be generated as shown in figure 7. A negative voltage is not necessarily needed to drive the LED. This is more a demonstration of how DC-DC converters can also generate negative voltages from positive voltages. Capacitor C<sub>1</sub> and diode D<sub>1</sub> level shift the positive peaks of the voltage waveform at pin 1 and clamp the voltage seen at the junction of D<sub>1</sub> and D<sub>2</sub> to a diode above ground. This now negative going waveform is rectified by D<sub>2</sub> and filtered by C<sub>2</sub>. Again a more efficient design would be to use Schottky diodes.
  
 {{ :university:courses:alm1k:alm-lab15_f7.png?500 |}} {{ :university:courses:alm1k:alm-lab15_f7.png?500 |}}
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 <WRAP centeralign>Figure 9 Adding negative feedback regulates the output voltage.</WRAP> <WRAP centeralign>Figure 9 Adding negative feedback regulates the output voltage.</WRAP>
  
-The regulated output voltage will be N times the V<sub>BE</sub> of Q<sub>1</sub> (a 2N3904 works well). The multiplication factor N is set by the resistor divider ratio. Using the 10 Kpotentiometer and the resistor values shown the output should be adjustable to a range of voltages around +5 V. The load regulation is fairly good up to the maximum current based on the chosen value for L<sub>1</sub> however, the temperature stability will be rather poor because of the strong negative TC of V<sub>BE</sub>.+The regulated output voltage will be N times the V<sub>BE</sub> of Q<sub>1</sub> (a 2N3904 works well). The multiplication factor N is set by the resistor divider ratio. Using the 10 KΩ potentiometer and the resistor values shown the output should be adjustable to a range of voltages around +5 V. The load regulation is fairly good up to the maximum current based on the chosen value for L<sub>1</sub> however, the temperature stability will be rather poor because of the strong negative TC of V<sub>BE</sub>.
  
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university/courses/alm1k/alm-lab-15.txt · Last modified: 30 Dec 2021 19:17 by Doug Mercer