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a few questions about Digital Step-Km Counter circuit/help


neverthought

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Hi friend
i have questions about below circuit & really need their answer soon
Stepcount.gif

R2________2M2  1/4W ResistorR4________1M  1/4W ResistorR5,R7,R8__4K7  1/4W ResistorR6_______47R  1/4W ResistorR9________1K  1/4W ResistorC1_______47nF  63V Polyester CapacitorC2______100nF  63V Polyester CapacitorC3_______10nF  63V Polyester CapacitorC4_______10΅F  25V Electrolytic CapacitorD1_______Common-cathode 7-segment LED mini-display (Hundreds meters)D2_______Common-cathode 7-segment LED mini-display (Kilometers)IC1______4093  Quad 2 input Schmitt NAND Gate ICIC2______4024  7 stage ripple counter ICIC3,IC4__4026  Decade counter with decoded 7-segment display outputs ICQ1,Q2___BC327  45V 800mA PNP TransistorsP1_______SPST Pushbutton (Reset)P2_______SPST Pushbutton (Display)SW1______SPST Mercury Switch, called also Tilt SwitchSW2______SPST Slider Switch (Sound on-off)SW3______SPST Slider Switch (Power on-off)BZ_______Piezo sounder]

R1,R3____22K  1/4W Resistor




























Questions
1.the function of D1 with considering D2 function

2.why pin"14" of IC2 is grounded by C4?

3.if Q2 be in cutoff ,how is the function of D1?

4.function of Q1 in circuit

5.how dose D2 count(show) 50 & 100 meters (full function description )

6.IC1D with which logic state enable the circuit?

if its possible please describe the circuit and its elements briefly

Device purpose:

This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot lights after every 50 meters of walking. A beeper (excludable), signals each count unit, which occurs every two steps. A normal step is calculated to span approx. 78 centimeters, thus the LED signaling 50 meters lights after 64 steps or 32 mercury switch's operations, the display indicates 100 meters after 128 steps and so on. For low battery consumption the display lights only on request, pushing P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together. Obviously this is not a precision meter, but its approximation's degree was found good for this kind of device. In any case, the most critical thing to do is placement and sloping degree of the mercury switch inside the box.

Circuit operation:

IC1A & IC1B form a monostable multivibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divide by 64. Q2 lights the dot of D1 every 32 pulses counted by IC2. IC3 & IC4 divide by 10 each and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each monostable count. Q1 drives the piezo sounder and SW2 let you disable the beep.

thanks

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Sorry, I can only answer questions 2 and 4 because the others are very poorly worded and don't make any sense.

2.why pin"14" of IC2 is grounded by C4?

C4 is a supply bypass capacitor, it reduces the impedance of the supply to higher frequency. Digital circuits tend to draw brief high current surges which will cause the supply voltage to momentarily drop; the capacitor acts like a little battery by supplying current during the surges, helping to keep the supply voltage up. Without the capacitor there is a risk that the circuit could become unstable due to fluctuations in the supply voltage.


There should ideally be a 100nF capacitor across the supply pins of each IC but you might be able to get away with using one electrolytic capacitor.

4.function of Q1 in circuit

Q1 turns on the piezo buzzer when pin 10n on IC1 goes low.

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thank you for answers
would you tell me about question 3
3.if Q2 be in cutoff ,how is the function of D1?

and other question
i think a little about question and searching

would you check my answer correct or complete them?

1.the function of D1 with considering D2 function?
Decade counter with decoded 7-segment display outputs drive D1 and after 9 digit pin"5" give out 1 and D2 show 1 Km

2.why pin"14" of IC2 is grounded by C4?C4 provide needed voltage for IC

3.if Q2 be in cutoff ,how is the function of D1?i do not know

4.function of Q1 in circuit?driving pizo sounder

5.how dose D2 count(show) 50 & 100 meters (full function description )?i just know 100m but not 50 m

6.IC1D with which logic state enable the circuit?it enable by low to high transition

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The "piezo sounder" is not a beeper, it is a transducer (speaker) that is driven at about 2.7kHz by the oscillator made from IC1C and driver transistor Q1.

C4 smooths the power supply voltage so it does not jump all over the place.

IC3 and IC4 are counter/decoder ICs. They do the counting and drive the displays.

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The "piezo sounder" is not a beeper, it is a transducer (speaker) that is driven at about 2.7kHz by the oscillator made from IC1C and driver transistor Q1.


I see, it's a Schmitt trigger oscillator.

The trouble is, it isnt' the correct way to drive a piezo which is a capacitive load. You ideally need a push-pull driver, otherwise it will be very quiet indeed.

As drawn, there is nothing to discharge the capacitive piezo transistor so it won't do much; moving R6 in parallel with the piezo will increase the volume by providing a discharge path.

Alternatively, get rid of Q1, R5 and R6 and connect the piezo directly to the output - it'll make the circuit simpler and louder.
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The trouble is, it isnt' the correct way to drive a piezo which is a capacitive load. You ideally need a push-pull driver, otherwise it will be very quiet indeed.

As drawn, there is nothing to discharge the capacitive piezo transistor so it won't do much; moving R6 in parallel with the piezo will increase the volume by providing a discharge path.

Correct. The transducer in this project is a coil and magnet speaker, not a piezo transducer.
RED does not have this project on his website anymore.
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