ILLUSTRATED MANUAL EN EDUCATIONAL LCD OSCILLOSCOPE WSEDU08 Whadda.
Build your own oscilloscope and learn how to visualize signals. See the signals you learn about in real life! Despite the low cost, this oscilloscope has a lot of features found only on expensive units like signal markers, frequency, dB, true RMS readouts,... A powerful auto-setup function will get you going in a snap! Note: This scope cannot be used to perform measurements on voltages higher than 30Vpp. Educational Input sensitivity range: in 6 steps, 100mV/division to 5V/division.
1. Assembly (Skipping this can lead to troubles ! ) Ok, so we have your attention. These hints will help you to make this project successful. Read them carefully. 1.1 Make sure you have the right tools: • A good quality soldering iron (25-40W) with a small tip. • Wipe it often on a wet sponge or cloth, to keep it clean; then apply solder to the tip, to give it a wet look. This is called ‘thinning’ and will protect the tip, and enables you to make good connections.
DO NOT BLINDLY FOLLOW THE ORDER OF THE COMPONENTS ON THE TAPE.
RESISTOR COLOR CODE 1st DIGITS 2nd 3rd Multiplier stripe Black 0 0 0 x1 10K OHM +/- 1% 100K OHM +/- 5% Brown 1 1 1 x 10 1st digit 2nd digit 3rd digit multiplier tolerance 1st digit 2nd digit multiplier tolerance 0.6 W Red 2 2 2 x 100 Orange 3 3 3 x 1 000 Yellow 4 4 4 x 10 000 Green 5 5 5 x 100 000 Blue 6 6 6 x 1 000 000 Purple 7 7 7 - Grey 8 8 8 - Tolerance 4th stripe 1% White 9 9 9 - Gold - - - x 0.1 5% Silver - - - x 0.
Construction Construction This educational LCD oscilloscope consists of three parts: the base PCB, the display PCB and the rear panel. First we assemble the display pcb and then the base PCB. On the display module we mount components on both sides. We start at the solderside and finish with the components on the component side. Display PCB 2 Ceramic Capacitors Solderside 1 Vertical resistors R...
Construction Base PCB 4 Diodes Watch the polarity! 2 ZD ... . ZD.. 8 5 Switch C... SW1 : on/off ZD1 : 5V1 6 Coil . (104) (104) (104) (104) (104) (104) L... . : 100nF : 100nF : 100nF : 100nF : 100nF : 100nF L. C11 C12 C13 C14 C15 C16 L1 : 100µH (1 - 0 - 1 - B) 7 (Gain) (Offset) Ceramic Capacitors C1 C2 C3 C4 C5 C6 C7 C10 Ceramic Capacitors c... . RV1 : 5K RV2 : 5K IC1 : 16p IC2 : 8p IC3 : 28p Zenerdiode Watch the polarity! c..
Construction 9 Vertical resistors R...
Construction 17 Mounting the test leads 18 Mounting the battery holder STEP 1: Strip both cables and twist the wire ends of each cable. STEP 1: Stick one part of the included hook-and-loop strap (hooks) on one of the long sides of the battery holder. STEP 2: Thin the wires. STEP 3: Mount both cables as shown in the drawing. - Tip: Start with one cable and then do the other. + Step 4: Solder the cables on the PCB.
Assembly ASSEMBLY STEP 1: Place the base PCB on top of the backside of the cardboard cover and trace the opening on the cardboard. M3 nut STEP 2: Stick the other part of the hook-and-loop strap (loops) in the centre of the traced area on the cardboard cover and put the parts together. Battery holder ho ok -a n (lo d-lo op op s) st ra p C ar d bo ar d 10mm M3 spacer Ba se PC B Bolts D is p la 2 x10mm M3 spacer y Remember to place 4 AAA batteries in the battery holder.
Calibration CALIBRATION Fine tuning of the input amplifier circuit requires a 1.5V battery. This calibration is optional. You must only do this, if you want a higher precision of your measurements. + To adjust the “Offset” trimmer RV2: - Connect the (+) of the test lead with the (-). - Press the Menu button. Use the down arrow button to scroll down to “Measure”. Use the right arrow button to select “Vdc”. Press the Menu button to return to the oscilloscope display.
Controls CONTROLS • Changing the volts/div. • Changing the setup mode in the setup menu. • Changing the position of the time markers during HOLD-mode. • Changing the timebase. • Scrolling up/down in the setup-menu. • Changing the position of the voltage markers during HOLD-mode. Changing the position of the trigger level during RUN-mode. Run / Hold Accepting the warning & Menu button ON/OFF slide switch: Slide in the upper position to turn on unit.
Turning on TURN ON At turn-on the splash screen below is displayed. IMPORTANT!: You should not attempt to measure voltages beyond 30Vp (=30VDC or 21VAC).If you are unsure if the voltage you’re about to measure is within the limits of the scope, then don’t measure it, or check with a multimeter first. Also: Never attempt to perform measurements on equipment that is powered from the AC grid without a transformer, e.g.
Test pin THE TEST PIN Connect the RED alligator clip to the pin marked ‘Test’. TESTPIN If your scope is working correctly, you should see a square wave displayed: Do not connect the BLACK BLA alligator clip. The test pin provides a square wave output with a frequency of approximately 2kHz (2000Hz). Note that the volts/div and time/div settings have automatically changed, to ensure a correct visualisation of the signal.
Menu THE MENU Press the MENU button to display the menu: Page 1: Page 2: UP and DOWN arrow buttons allow you to scroll trough all menu items on page 1 and 2. LEFT and RIGHT arrow buttons allow you to change the settings. Press MENU button again to leave menu and enable your selection. MENU ITEMS: Volt/Div: Select the appropriate V/div setting. Available setting are: Time/Div: Select the appropriate Time/Div setting. Available setting are: AUTO Volt 0.1V/div 0.2V/div 0.
Menu Coupling: Select the desired input coupling: Show: Select the vertical marker readout: • AC: Only the AC-component of the signal is displayed • DC: Both the AC and the DC component of the signal is displayed • Time mark: Display time between the 2 vertical markers • Freq mark: Display the frequency in Hz of the part of the signal between the 2 vertical markers Trigger: Turn on or off the trigger function. (Note: When AUTO Volt and/or AUTO time is selected, triggering is also set to AUTO Trg).
Let’s measure LET’S MEASURE Measuring DC voltage: Measuring a 9V battery (not incl.) First, make sure that your scope is properly calibrated (see page 12). • • • Open the menu, scroll down to Measure and select Vdc. Now, swap both alligator clips and check what happens: Leave the menu and watch the lower right hand corner: This is a nice feature of an oscilloscope, it can measure both positive and negative DC voltages. Turn on the scope. Connect the alligator clips to the battery. Mind the polarity.
Let’s measure Displaying and measuring waveforms: We have a nice waveform available at the test pin, it is perfect for our measurements. Turn off the scope, connect the red alligator clip to the ‘test’-pin and turn on the scope. Now the position of the waveform changes, as the DC component of the signal is blocked. The scope only displays the AC part, which is both positive and negative.
Let’s measure Triggering and how to use it: Triggering helps us to get a stable trace on the screen and it also allows us to capture events. If you move the trigger level to a point lower than the signal, the scope will no longer refresh the trace, as the trigger level is no longer reached. When ‘AUTO Volt’ and ‘AUTO time’ is enabled, the scope triggers automatically. To enable manual triggering, select 0.
Let’s measure Look closely at the signal now (left), do you see the difference with the previous screenshot of our signal (right)? Single: Next, leave the menu and set the trigger level as shown below: Sometimes, you would like to ‘capture’ a certain event, instead of continuously looking at a signal. This can be done by choosing ‘Single’ instead of ‘Run’ as the Run mode.
Let’s measure The display will look more or less like below: Now, touch the red alligator clip with your finger. Your body acts like an antenne and touching the clip will induce ‘noise’ to the input of the scope. The unit will trigger and the display will show a single screen of the noise you’ve injected trough your finger. Next, the scope will switch to ‘HOLD’mode. Now you have plenty of time to study the screen. To capture the next event, press the ‘HOLD’-button briefly.
Oscilloscope Terminology 1. Volts/div: Determines how many volts the signal at the input must swing for the trace to move one division. 2. Time/div: Determines the time the trace needs to scan from the the left hand side to the right hand side of a division. 3. Division: Imaginary or visible grid on the oscilloscope screen. It helps estimating signal amplitude and period. 4. Period (T): Duration of one cycle of the AC waveform (= 1/f). 3 5.
Oscilloscope terminology Clipping: When the ‘top’ or ‘bottom’ or both extremes of a signal are cut-of (‘clipped’), e.g. because the signal cannot swing any further due to power supply limitations. An undesired property of amplifiers that are driven beyond their specs. Also happens when a too small Volt/div setting is selected or the signal the input of the scope is beyond the specs. DC coupling: The oscilloscope displays both the AC and the DC component of a signal.
Oscilloscope terminology Noise: Undesired random addition to a signal. Ripple: Unwanted periodic variation of a DC voltage. Rising or falling slope: It determines where the scope will trigger. This can be on the rising or on the falling slope of the signal. falling slope rising slope RUN or RUN-mode: When in RUN-mode, the screen is continuously updated with new data. Sample rate: Usually expressed in samples or megasamples/second, sometimes in MHz.
PCB BASE PCB 25
PCB DISPLAY PCB 26
PCB DISPLAY PCB 27
Diagram 28
Leds and how to use them Never connect leds in parallel Leds feature a specific voltage drop, depending on type and colour. Check the datasheet for exact voltage drop and rated current ! How to Calculate the series resistor: Example: operate a red led (1.7V) on a 9Vdc source. Required led current for full brightness: 5mA (this can be found in the datasheet of the led) Supply voltage (V) - led voltage (V) = series resistance (ohms) required current (A) closest value : use a 1k5 resistor 9V - 1.7V 0.
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