Using ER1211 ASIC as automatic exposure controller circuit diagram

As shown in the figure, the ER1211 special integrated circuit is used as an automatic exposure controller circuit . ER1211 is an automatic exposure . The pin arrangement is shown in Figure (a), ① is power supply voltage monitoring, ② is low illumination monitoring, ③ grounding, ④ illumination warning output, ⑤ relay drive output, ⑥ exposure delay device, ⑦ exposure delay input, ⑧ Automatic focus control, ⑨ exposure control, ⑩ power supply Vcc.

The rated operating voltage of ER1211 is 3V, but it can still work normally when Vcc ≥ 2.1V, and the exposure delay error is not greater than ±5%; and when Vcc < 1.7V, the circuit stops working. The relay does not operate, the mechanical actuator is locked, and the shutter cannot be pressed.

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The ER1211 application circuit is shown in Figure (b). The shutter button K2 is linked to the power switch K3. When the shutter button is pressed halfway, K3 is turned on and the capacitor C1 is charged. When the voltage on C1 is charged to Vcc, the ⑤ pin outputs a low level, causing the Relay J is closed and the shutter is in ready state. When the shutter button is fully pressed, the shutter is mechanically released offline, the shutter blade is opened, and the exposure begins I. At the same time, the switch K2 is controlled to be turned off, and C1 is discharged through the potentiometer W, the photoresistor cds and the resistor R2, so that the potential of the ⑦ pin Gradually decrease, when C1 is discharged to the point where the potential of pin ⑦ is lower than the potential of pin ⑥ of the exposure delay preset, pin ⑤ outputs a high level, causing the relay J to release, the shutter blade closes, and the exposure ends.

When the shutter button K2 is pressed halfway, if the illumination of the subject environment is lower than the limit value (V2≤V6-0.2V), pin ④ will output low level, and the low illumination warning light LED will light up. The selector switch K- linked to the flash is connected to position A when the flash is turned on. Correspondingly, C1 is discharged through W and R1, and the exposure time (discharge time) is fixed, even if the flash automatic metering circuit does not work.