A/V switcher

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myp71
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A/V switcher

Post by myp71 » Mon Mar 07, 2005 3:30 pm

I was wanting to build a A/V switcher for like security cameras that would switch between the four cameras automatically. I was thinking that I could use the guts from a A/v switcher from like Bestbuy that you would use for like to switch your playstation & dvd player ...etc over. I have seen two different switchers like this one model has a remote that you can switch without getting up or the other model that you have to push a button to get the right video on the TV. which "model" would it be easier to make it into a auto switcher with a timer? Also if I could I would like to have the one with the remote so if I wanted to keep a camera from switching i could use the remote.<p>Thanks for any help <p>Ryan

Bernius1
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Re: A/V switcher

Post by Bernius1 » Tue Mar 08, 2005 5:37 am

I've seen bilateral switches like the CD4016 & CD4066, in SMD with hi-freq range. And there are newer bi-lat switches specifically for video. Of BJ's has the whole sh'bang for $300>$400 , B&W w/CCD's.
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philba
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Re: A/V switcher

Post by philba » Tue Mar 08, 2005 8:50 am

Video sequencers (that's what you described) are pretty cheap. I picked up my 4 camera sequencer 3 years ago for about $80 - it also does quad display (4 1/4 size images at once). Fry's has them around that price and I recall seeing similarly priced ones elsewhere. Here's one for $60 - I dont know how good it is... http://www.surveillance-video.com/noname11.html<p>Of course, depending on features, you can find products that cost way more.<p>If this is a case where you are looking to save money, you'll be hard pressed to beat the off the shelf price at the low end.<p>[ March 08, 2005: Message edited by: philba ]</p>

Dean Huster
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Re: A/V switcher

Post by Dean Huster » Tue Mar 08, 2005 5:21 pm

You could like maybe check out Maxim at http://www.maxim-ic.com who make like some pretty neat analog video switcher ICs made just for that purpose. And Analog Devices at http://www.analog.com like makes similar switches, but they aren't quite as like easy to get free samples from as Maxim. I don't remember if Linear Technology at http://www.linear.com like make some of those, but they'd be like good to check out, too.<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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myp71
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Re: A/V switcher

Post by myp71 » Thu Mar 17, 2005 10:14 am

Thanks for the help.<p>I found a AV switcher for different video game systems and it has a remote that you can flip between four different AV inputs. Do you think that I could put a timer on that some how? Maybe by using the remote to transmitt the siginal?<p>
Thanks again Ryan

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philba
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Re: A/V switcher

Post by philba » Thu Mar 17, 2005 1:57 pm

sure, but I'd open it up, try to figure out where the swtch channel signal goes and hook up a simple astable timer (555) to pulse it. Then you a) dont have to hack up the remote and b) have a self-contained solution.

myp71
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Re: A/V switcher

Post by myp71 » Thu Mar 17, 2005 4:04 pm

Thank you.<p>Would I need to look at the unit first before I could get a circuit for the 555 timer? Or how would that work? <p>Ryan

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philba
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Re: A/V switcher

Post by philba » Thu Mar 17, 2005 7:15 pm

First a disclaimer - I haven't looked at this unit so use your common sense ahead of anything else.<p>Tools - screw drivers, a decent DMM, a magnifying glass and, optionally, an o'scope. A loup and logic probe would be good, as well.<p>With the unit unpowered, I'd first open it up - carefully as not to break the case. Find the power supply and identify +V and ground - especially a place to clip on the "-" lead of your DMM. <p>Does the unit have a button to switch the channels? If so, follow the button to see if there is a pull-up or pull down resistor (probably 10K). Pull-up means it ties +V to the signal, pull-down means it ties gnd to the signal. If its a pull-down then you could use a 555 to directly switch the signal. If its a pull-up, you'll need to invert the output of the 555 (via a simple transistor, I'd guess) to get it right. You can also determine pull-up or down by using your DMM to measure resistance from each side of the switch to ground and +v. Pull up with have one side with moderate resistance, say 10K or so, to +v and 0 ohms to ground on the other side of the switch. Pull down will be similar but 10K to ground and 0 to +V. <p>If there is no button, you'll need to trace out the IR receiver and figure out where the switch logic is.<p>Once you have determined pull up or down, time to test it. Clip on a wire to pull-up side (or pull down side) of the switch. Carefully, power up the unit, making sure there are no shorts. Then, touch the wire to ground (or +V). The unit should switch channels. If it works, that's where you'll attach the timer output as discussed above. <p>I'd look for a place to put the timer circuit inside the case and run a switch to allow you to disable it. I'd also consider using a small pot to control the switch rate.<p>edit: oops. you dont need an inverter. the 555 by itself shoudl work ok.<p>[ March 17, 2005: Message edited by: philba ]</p>

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