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Old 9th March 2008, 05:48 AM   (permalink)
Default Help with transistor as switch

I have some knowledge of digital circuits, but not much in the way of analogue circuits so I'm stuck on this.

Here's what I have: A digital camera infrared remote. I want to be able to "press" a buton on this camera remote remotely, ie RF so I don't need a direct line of sight.
I also have one of those remote (RF) controlled noise machines that I'm trying to use to trigger a button on the camera remote.

I've taken apart the camera remote, and soldered two wires on the contact of the button.. so that if I short the wires the button on the camera remote button gets "pressed".
My problem is I'm not sure how to attach these wires to the noise machine so that when I use the RF remote for the noise machine, the camera remote button gets "pressed".

Simply attaching these wires to the two speaker wires on the noise machine doesn't work, as this causes camera remote button to always be pressed.

I think a transistor might be whats required, but I'm not sure how to set it up. I've found some schematics of transistors as switches on the internet, but it seems my case is a bit different.

Anyone have any ideas? Thanks
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Old 9th March 2008, 12:57 PM   (permalink)
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Well, It's a long shot but I think I see what you're after here.

Use your RF remote to drive the transistor which triggers a Reed Relay, Use the relay contacts to 'contact' your camera button.

hackableFM...
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Old 9th March 2008, 03:00 PM   (permalink)
Default analog switches

so what you'd like to do is an analog switch on the IR remote control and this analog switch is actually controlled by the RF remote control ?

well I am not quite sure but this press button on the IR remote control all it does is a pull down which you can actually do with an MCU (provided there is not a lot of current flowing in at this port). I guess you already need an MCU as an interface at the RF receiver so you can use one of its pins as a pull down ...

hope this helps
Antonio
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Old 9th March 2008, 07:33 PM   (permalink)
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All I really need is a way to electrically connect two wires (which trigger the button I want on the camera remote) when sound comes out of the speaker on the noise machine. The two wires are right next to the sound machine.
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Old 9th March 2008, 09:53 PM   (permalink)
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Quote:
Originally Posted by sabotaged
I have some knowledge of digital circuits, but not much in the way of analogue circuits so I'm stuck on this.
I envy you so.

Anyways. THe two wires you need to electrically connect- is it DC Or AC going through them? And what frequency and how fast do you need to connect them at?

Last edited by dknguyen; 9th March 2008 at 10:03 PM.
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Old 9th March 2008, 11:00 PM   (permalink)
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Quote:
Originally Posted by dknguyen
I envy you so.

Anyways. THe two wires you need to electrically connect- is it DC Or AC going through them? And what frequency and how fast do you need to connect them at?
It's DC. Only about 2.6V between them. They need to be connected for about 1 second, which is coincidently about the same amount of time the noise machine is active for when triggered.
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Old 10th March 2008, 02:11 AM   (permalink)
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Quote:
Originally Posted by sabotaged
It's DC. Only about 2.6V between them. They need to be connected for about 1 second, which is coincidently about the same amount of time the noise machine is active for when triggered.
You may connect the transistor's collector to the positive wire of the camera's input.

The negative wire from the camera's input, the transistor's emiter and one side of the noise machine's speaker are tied together - you may think this connection as the circuit's "ground"

The other side of the speaker goes to a small diode (1N4148) to rectify the "noise" and then to the transistor's base.

If "They need to be connected for about 1 second" add a capacitor between the transistor's base and the "ground" (emiter) to convert the rectified AC into DC.
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Old 10th March 2008, 05:17 AM   (permalink)
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Quote:
Originally Posted by ecerfoglio
You may connect the transistor's collector to the positive wire of the camera's input.

The negative wire from the camera's input, the transistor's emiter and one side of the noise machine's speaker are tied together - you may think this connection as the circuit's "ground"

The other side of the speaker goes to a small diode (1N4148) to rectify the "noise" and then to the transistor's base.

If "They need to be connected for about 1 second" add a capacitor between the transistor's base and the "ground" (emiter) to convert the rectified AC into DC.
I just tried this, but the camera wires aren't closing together when the sound device activates. If I swap the camera wires then it's always activated (which I think it's because it's connected backwards through the transistor in that case?)

Edit: I just tried another transistor and now it's working. Thanks!

Last edited by sabotaged; 10th March 2008 at 10:01 PM.
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