ELM307 Просмотр технического описания (PDF) - Elm Electronics

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ELM307

Camera Control

Elm Electronics 

ELM307

Example Applications

Figures 1 and 2 show two typical circuits that the

ELM307 can be used in. The first is labelled ‘Party

Camera’ but really applies to any candid situation

where a switch is used to initiate the picture being

taken.

Although both circuits show a 3V battery for a

supply, this is only for portability. Any convenient

supply that is between 3V and 5.5V could just as

easily be used. Note that both supplies are bypassed

with 0.1µF capacitors. This is good practice, but could

be eliminated if cost is a concern, and the battery is

electrically close to the ELM307.

In Figure 1, PW and Delay are both at a high

level, so the circuit is configured for a 1 second ouput

with a minimum delay of 5 seconds between outputs.

An NPN transistor (2N3904 or similar) provides the

interface to the camera. Fortunately most cameras

these days (including disposables) use a momentary

contact for the shutter control, and this transistor can

simply be connected across that button to initiate a

picture. You may have to experiment a little to get the

polarity correct, though. An additional 33KΩ resistor is

shown connected in series with pin 5 to provide some

protection from electrostatic discharges. This is a

good idea if the initiating contact is located more than

a few feet from the ELM307. Note that there is no

3V +

power

0.1µF

1

8

2

7

3

6

4

5

+3V

33KΩ

33KΩ

AM radio

headphone

output

2.2KΩ

15Ω

Figure 2. Lightning Detector

3V +

power

1

2

3

4

+3V

0.1µF

8

7

6

5

33KΩ

(see text)

33KΩ

33KΩ

Figure 1. Party Camera

initiating

contact

Camera

shutter

control

resistor required in series with the LED in this circuit,

as internal circuitry limits the current to a safe value. If

a higher supply level is used, a small value resistor

(220Ω) should be connected in series with the LED.

The circuit shown in Figure 2 can be used to

capture photos of lightning (as long as the camera’s

inherent delay in responding is not so great that the

flash has dissipated). Some cameras have a

considerable delay in opening the shutter after

Camera

shutter

control

the button is pressed, and may not be

acceptable for this use.

The circuit shown is virtually identical to that

of figure 1, except that an additional NPN

transistor has been connected to amplify the

output of an AM radio and trigger the circuit.

In operation, the ELM307 is placed in the test

mode, the AM radio is tuned between stations, and its

volume is adjusted to trigger the LED only on lightning

flashes. When ready, the pushbutton is held for 3

seconds then released, switching the circuit to the run

mode. Hopefully the camera is pointing in the right

direction when a flash is detected.

Many variations on these circuits can be used to

trigger a camera, only limited by your imagination.

Why not connect an ELM460 for a 200sec period,

feed it into the ELM307 trigger, then put everything on

a kite and go fly it…

ELM307DSA

Elm Electronics – Circuits for the Hobbyist

< http://www.elmelectronics.com/ >

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