A novel resonance demonstration device

This circuit consists of a multivibrator and a power amplifier driving circuit as shown in the figure.

The frequency-adjustable multivibrator composed of NE555 and peripheral components generates a frequency-adjustable rectangular pulse signal, which is output from the "3" pin of NE555 and added to the base of the power amplifier tube VT through the current-limiting resistor R2. The collector load of VT is the relay electromagnetic coil K. Under the control of the NE555 rectangular pulse, VT works in the switching state.

The coil of the relay can generate a periodic attraction, which is the driving force, so that the three vibration systems fixed on the armature are acted upon by the driving force. When the frequency of the driving force is the same as the natural frequency of one, the amplitude of that one is the largest, otherwise, the amplitude is very small.

Diode VD is the discharge path of coil K to protect VT.

Production and debugging

(1) Remove the outer shell of relay K to expose the armature part. Glue a flat plate on top of it to fix three spring leaves on it. Drill a hole at the bottom of each spring leaf for adding counterweight during debugging.

(2) After the circuit is connected, fix the relay and its vibration system on the bracket so that the three vibration systems can swing freely and the armature can be freely attracted and separated after being energized. That is, the added armature limit device must be appropriate.

(3) First debug the one with the lowest frequency, adjust the vibration frequency of NE555 to the low end, that is, adjust the potentiometer RP to near the maximum value, use the longer spring (if the three springs are of different lengths), and adjust the added counterweight to maximize its amplitude.

(4) Then adjust the middle resonant frequency, reduce the resistance of the potentiometer by about 10 to 20k, use a spring with a middle length, and adjust the added counterweight to maximize the amplitude.

(5) Finally, adjust the one with the highest resonant frequency, adjust the resistance of the potentiometer RP to a smaller position, use the one with the shortest spring length, and adjust the added counterweight to maximize its amplitude.

At this point, the debugging of the entire device is completed.

How to use

(1) Before power is turned on, each vibration system is manually vibrated separately. Of course, they are all vibration reduction systems, but their vibration frequencies are different, which are their respective natural frequencies.

(2) After power is turned on, use the potentiometer RP to adjust the frequency of the NE555 multivibrator.

When the frequency of the driving force generated by NE555 is equal to the natural frequency of a vibration system, it can obtain the maximum amplitude, that is, resonance occurs, while the amplitude of the vibration system without resonance is very small or almost does not swing.

Points to note: The natural frequencies of the three vibration systems should not have double frequencies as much as possible.