Camera Circuits
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One leg of the photocell (Rl) is tied to the +15 volt supply and the other end is connected to ground through resistor R2, forming a voltage-divider network. The non-inverting input of the 741 op amp, IC1, is tied to the junction formed by Rl and R2, while its inverting input is grounded through resistor R3. When switch SI is pressed, another divider network is formed, reducing the voltage applied to the inverting input of the op amp. When... .
The circuit arrangement consists of a photo-amplifier which feeds a voltage derived from varying light levels in an enlarger to a pair of peak detectors. One follows the peak positive voltage and the other the peak negative voltage. The capacitors used for storing the voltage peaks in the followers also form part of sample and hold circuits which are then switched to hold after the measurement. Their outputs represent the maximum and minimum... .
The darkroom timer/controller uses few external components: a display, a digit driver, keyboard, and output switching devices. A 4-digit common-cathode LED display is desirable for dark room environments. The time base is provided by shaping up the 50/60 Hz ac line. A DPDT switch (Si) is used to select a resolution of or 1 seconds and to simultaneously move the decimal point .
This circuit gives multiple "stop-action" photographic effects like showing a bouncing ball in up to nine locations in a single photograph. The circuit will automatically fire the bulbs sequentially with the time between each firing variable. The circuit is functionally complete except for the actual firing system. In many cases, a simple SCR will work, as shown. The firing can be initiated in one of two ways .
Take strobe-flash pictures the instant a pin pricks a balloon, a hammer breaks a lamp bulb or a bullet leaves a gun. Use a transistor amplifier of 1-watt rating or less. (It must have an output transformer) The amplifier is terminated with a resistor on its highest output impedance, preferably 16 ohms .
Transistor Ql is a light-activated silicon-controlled rectifier (LASCR). The gate is tripped by light entering a small iens built into the top cap. To operate, provide a 6-in. length of stiff wire for the anode andcathodeconnections and terminate the wires in a polarized power plug that matches the sync terminals on your electronic flashgun (strobelight). Make certain the anode lead connects to the positive sync terminal .
You can set the interval from about 5-30 seconds. A relay operates the slide-change mechanism. Op amp Ul forms a sort of Schmitt trigger. Resistors Rl and R2 bias the noninverting input at pin 3 of Ul to half the supply voltage. Feedback resistor R3 increases or reduces the bias to pin 3, depending on whether the output of Ul is high or low. When power is first applied to the circuit, C2 has a zero charge and the inverting input of the op... .
Transistor Ql remains off until the magnetic switch connected to Jl closes. When that happens, the 9 Vis connected through Rl to Ql"S base. Ql turns on, thereby charging C2 through relay Kl, which causes Kl "s contacts to close. Since the contacts connect viaJ2 to the remote control jack in the camera, which in tum connects to the camera"s shutter release, the closure of Kl"s contacts will cause the camera"s shutter to trigger. After C2... .
The NE555 circuit is a basic one-shot timer with a relay connected between the output and ground. It is triggered with the normally open momentary contact switch, which when operated, grounds the trigger input at pin 2. This causes a high output to energize Kl which closes the normally open contacts in the lamp circuit. They remain closed during the timing interval, then open at time out. Timing is controlled by a 5-M!lpotentiometer, R,.... .
Insulated-gate, field-effect transistor (IGFET), Q2 and silicon photo cell Zl form the heart of this circuit. Transformer T1 is an audio-output type, but it"s reversed in the circuit. A sudden flash from a photoflash unit detected by Zl sends a voltage pulse through the low-impedance winding of Tl via Rl. That voltage pulse is stepped-up in Tl"s 500-!l, primary winding before being rectified by Ql. Transistor Ql is used as a diode; its... .
This circuit is used for remote photographic flash units that flash at the~ame time as the flash attached to the camera. This circuit is designed to the trigger cord or hot shoe connection of a commercial portable flash unit and triggers the unit from the light produced by the light of the flash unit attached to the camera. This provides remoteoperation without the need for wires or cables between the various units. The flash trigger unit... .
This circuit will record commentary and/ or music on one track of a tape and put the beeps that change the slides on another track. Gate U2a is used to trigger U1, which is configured as a timer when a pulse is received from either the tape input or via pushbutton switch Sl. Timer U2 outputs one pulse for every input pulse received, no matter how long S1 is depressed. The Q output of U2 at pin 1 is fed to U2b, which is set up as an... .
Using the CA3164A BiMOS control chip consumes less than 15 pA during standby, yet it can provide 100 mA of chopped current to the de-to-de converter during the energy-reservoir charging cycle. The CA3164A drives tbe primary of T1 with symmetrically chopped current at a 400 to 2000 Hz rate. The CA3164Ns chopper frequency is about 500Hz; .
Meter Ml, a +/-50-uA zero-center D`Arsonval meter movement is driven by Ul, a TL081 FET op amp, through R3. The gain of Ul is set at 11 by Rl and R2, while capacitor 01 is used to restrict the bandwidth of Ul to 1.6 Hz. Power for the circuit is derived from a simple dual-polarity 12- V power supply (consisting of Tl, D3, D4, 02, and 03). A light-dependent resistor (LDR), R16 (which is a semiconductor element whose resistance decreases as it... .
The electronic darkroom timer is built around a 555 oscillator/timer, a pair of general-purpose transistors, a buzzer, and an LED. The 555 (Ul) is configured as an astable multivibrator (free-running oscillator). The frequency of the oscillator is determined by the values through i3 and Cl through C4. Switch SI is used to divide the capacitor network to vary the time interval between beeps; when SI is closed, the circuit beeps at intervals of... .
Two gates of a 4011 arc used as a comparator. When the resistance of R4 decreases the voltage at pin 1 and 2 increases, producing a logic zero at pin 3, causing pin 4 to go high and activating the LED. R3 is calibrated in light units, or seconds exposure time. To calibrate, set pot R3 so as to just be on the LED ON/OFF threshold. With a light level that is suitable to correctly expose a photographic print, .
This circuit can be used for multiple cameras with one monitor. The circuit can be operated manually or automatically. .
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