LONG LIFE BATTERY-BR9V DC battery
BR9V DC battery
QI - Photosensitive Transistor
Ei - 100kQ1 / 2w carbon film resistance diagram' 34 automatically adjusts the installation position of transistor qi in photo transistor swing 35 of commercial advertisement broadcast.It is installed in a small hole in the box so that its photosensitive surface can be directly irradiated by the light beam.Transistor QI has three leads, but only two of them are used in this circuit, and its third base lead can be cut off.
4 - 31 Debugging Steps
Before loading the circuit board into the box, connect the battery and the phototransistor, and conduct preliminary debugging. This is a very simple step and does not require any special instrument, as long as there is an ohmmeter, it can be debugged.
Connect the ohmmeter to the output lead of the relay and cover the light-transmitting window of the phototransistor. The reading of the ohmmeter should be zero ohm.However, if its reading is not zero, but infinite, it must be the wrong connection. If one of the leads is mistakenly connected to the normally open contact instead of the normally closed contact, the lead can be switched and re - debugged.When the meter reads zero, the connection is correct.
Then take off the cover of the phototransistor and aim the phototransistor at the light source, and hear the relay " clatter" sound, then the ohmmeter reads infinity d if this is not the case, the relay is not operating, possibly because the battery is out of power.It can be checked with a voltmeter, and if it is confirmed that the battery is not charged, it can be charged or replaced with another one.Other possible reasons for not working are the installation of transistors, the quality of relays, or the wrong connection of batteries.If the positive and negative poles of the battery are reversed, one or two transistors may be damaged.After the battery is connected reversely, triode 2 is the most easily damaged, so it must be checked first. If it is damaged, replace it with another one.
The method of connecting the lead wire of the relay contact to the TV speaker is very simple. First, cut the lead wire that was originally welded to one terminal of the speaker, that is to say, cut off a connection between it and the audio amplifier.Then two leads are led out from the relay and connected to both ends of the disconnection.And welded up and wrapped up with insulating tape.When the circuit is not illuminated by light, the speaker emits sound.When light hits the surface of the phototransistor, the relay disconnects the connection line between the audio amplifier and the speaker, and the speaker stops broadcasting.In order to protect the phototransistor from the normal indoor light, it is necessary to use a k paper symbol
Figure 4 - 36 Installation of Shading Hard Sheet Paper Tube and Photosensitive Transistor
A small cardboard ring or cylindrical object shields the light 3 for it as shown in fig. 36.If you want the circuit to work, just direct a bright flashlight beam at the cylindrical opening.
The rated current of relay contacts used here is 115V AC 1A. It must be noted that many TV sets have a higher rated current than it, so this switch-off circuit can only be used to cut off the speaker and not to cut off the power supply.If you want to cut off the power supply, you must switch to a relay with a large capacity contact.Or, as described above, the through contacts control the power supply to drive the relay.
4 - 32 Sound Exposure Meter
The simple exposure meter circuits described earlier in this chapter use meters to indicate the brightness of light.The circuit shown in figs. 4 - 37 is not indicated by a meter, but by an audible " click" sound.
The main significance of this circuit is experiment rather than practicality, but this is indeed an interesting experiment in the sense of the energy conversion process from light energy to electric energy and then to acoustic energy.This circuit can also be used as a light-controlled metronome and counting device.
B - 9V battery
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Figure 4 - 37 Audio Exposure Meter Circuit
Figure 4 - 38 Installation of Components on Circuit Boards and Boxes