Bauteile

Voltage Characteristics Of Z-diodes

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Z-Diodes are often used for simple voltage stabilized circuits. It is very important to use the Z-diode with the correct parameters.
This article shows an example for the voltage characteristics of two Z-diodes.

The reverse voltage of a Z-diode depends extremly on its reverse current. In data sheets the Z-voltage is given for a given reverse current.
If the reverse current is much more different than that value the Z-voltage is very different.

The following figures shows the Z-voltage over the reverse current from 0.5..30 mA of two Z-diodes with a nominal Z-Voltage of 2.7 V

comparison of two 2.7 V Z-diodes at 5 mA
Figure 1: comparison of two 2.7 V Z-diodes at 5 mA reverse Current

Figure 1 shows that both Z-diodes have their nominal Z-voltage at a reverse current of about 5 mA.

Comparison of two 2.7 V Z-diodes
Figure 2: Comparison of two 2.7 V Z-diodes

Figure 2 shows the whole voltage characteristics. It shows that at 2.5 mA the Z-voltage is only at 2.5 V. At 10 mA the voltage is at 2.9..3 V.

Tutorials

Generation Of Saw Tooth Or Triangular Voltages With SwitcherCAD

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One who needs to simulate a circuit will sooner or later stumple across SwitcherCAD. This article shows how to generate a saw tooth or triangular voltage.

The company Linar Technology provides on its web site the tool SwitcherCAD for free.
It is a Spice base simulation tool that is uses to simulate curcuits. Unfortunatly it is only available for the Windows platform.

Generations Of Saw Tooth Or Triangular Voltages

From the component dialog choose a voltage source “voltage” and place it in the schematic with OK.
SwitcherCAD component dialog
With a right click on the voltage source in the schematic open the dialog für the voltage source.
SwitcherCAD voltage source dialog
In this dialog click on Advanced to open the advanced dialog.
Choose the function “PULSE”. To generate a saw tooth the parameters “T rise” “T fall” “T on” and “T period” are important.
For this example we want to generate a saw tooth with 20 Hz.
“T period” needs to be 50 ms.
“T rise” could be set to 50 ms and “T on” and “T fall” to 0, but this can leed to strange simulation results. It has been proved to set “T on” and “T fall” at least to 1 ns and substract this times from “T on”. The result must be entered for “T raise”. Of course you need to enter a value for “Von” higher than 0 to have a voltage that can be measured.
SwitcherCAD voltage source dialog advanced
The result should then look like this:
SwitcherCAD sawtooth voltage source
SwitcherCAD sawtooth voltage plot

To generate a triangular volage only a little modification is necessary. “T raise” will be set to 25 ms, “T on” to 0 and “T fall” will also set to 25ms.
SwitcherCAD triangular voltage plot

Akkus

Observations On Batteries

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This article takes a look on the costs of batteries compared to accumulators and additional chargers.

Energie costs

Batteries are one of the most expensive energie sources.
Lets make a calculation:

  • Battery: Alkaline, size: AA
  • Voltage: U = 1.5V
  • Capacity: K ≈ 2Ah

For one battery the stored energy is:

E = U ⋅ K = 1.5V ⋅ 2Ah = 3Wh

To get one kilowatthour energy out of batteries you need:

1kWh = 333 Batteries
3Wh

If one battery is 1,00 € then per kilowatt hour you pay:

333 peaces ⋅ 1,00 €/peace = 333 €/kWh

In comparision one kWh out of solar energy that is currently payed with 0,57€ is indeed cheap.
So it makes sense to use accumulators and a good charger if you use equipment with high energy demands like digital cameras or remote controlled model vehicles.

Today there are size AA accumulators that have a capacity of more than 2500 mAh. With a durability of 1000 charge cycles that can be achieved with a good charger that means a accumulator can provide 2500 Ah during its live span.

The accumulator voltage is 1.2 V. That results in 3 kWh energy during live span. If the accumulator costs 5,00 € and the charger is 40,00€ then the costs per kWh are:

45 € / 3kWh = 15,00 €/kWh

If you use more than one accumulator the costs decrease even more:

for  4 accumulators: 60€ / 12kWh = 5,00€/kWh

Of course there are the costs for the electrical energy from the grid. For 0,20 € per kWh this are 2,40 €, in sum this is for 4 accumulators  7,40 €/kWh. The losses when charging and self discharge losses of the accumulators are neglected for this observations.