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TomT
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Re: Do It Yourself: 240v from two 120v sources

Mon Jun 13, 2011 10:43 pm

What did you use for the buzzer?

Thanks!
Ingineer wrote:Here's a quick schematic of a basic safe unit:
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Ingineer
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Re: Do It Yourself: 240v from two 120v sources

Mon Jun 13, 2011 11:08 pm

mogur wrote:What did you use for the buzzer?

Thanks!
Ingineer wrote:Here's a quick schematic of a basic safe unit:
I don't have a schematic drawn for that feature. Basically the same power supply arrangement as shown for the LED, but an added piezo buzzer driven by a 555 timer configured as a one shot. It runs a few seconds when powered up on 240v, then goes silent. This way you know instantly when you've found the right 2 outlets without having to look at the LED. It also doubles as a power restored alarm in the event the power goes out and comes back on. =)

Update: See post below for schematic with buzzer feature.

-Phil
Last edited by Ingineer on Tue Jun 14, 2011 2:37 am, edited 1 time in total.
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Re: Do It Yourself: 240v from two 120v sources

Mon Jun 13, 2011 11:55 pm

Ingineer wrote:Image

-Phil
Cool! Thanks Phil!
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Re: Do It Yourself: 240v from two 120v sources

Tue Jun 14, 2011 2:08 am

Now, it'd be great if somebody who will try to build this device can document where they buy their parts from so that we can just follow their footsteps instead of trying to hunt all over the place for parts. I understand the schematic and I think I can build from it, but I'm really not familiar with where to go to get parts.

Another option is if somebody wants to assemble all the parts and sell them out as a DIY kit for a profit. That way the labor for the assembly is on the buyer.
Last edited by Volusiano on Tue Jun 14, 2011 4:30 am, edited 1 time in total.

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Ingineer
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Re: Do It Yourself: 240v from two 120v sources

Tue Jun 14, 2011 2:35 am

Ok, I added the Buzzer:

Image

Once connected to 240v, the Blue LED will light, and the buzzer will sound for about 3 seconds then it will silence. If you wish to change the time the buzzer stays on, simply change the value of C4. The value in microfarads roughly equals the time in seconds the buzzer will sound. All the capacitors in the timer circuit should be rated for 25v. Zener Diode ZD1 is 12v @ 1w, and BUZ1 needs to be a low-power 12v Piezo buzzer. The one I used is a Projects Unlimited PI-256K.

There is also a toggle switch (S1) that lets you select between 120v and 240v output. If you don't want it, simply jumper connections 1 and 2 together and don't use 3. If you do add the switch, it must be rated for your load, I recommend at least 25A.

For safety, It's very important to use a 10ohm 1watt flameproof or fusible resistor for R1 and that C1 be .22uF and a minimum of 300 volts. (you can go higher on capacitor voltage, but never lower!)

I do not recommend anyone attempt fabrication of this project unless they are qualified to work on electronics and high voltages. All parts in the circuit are connected to potentially lethal line voltages!

-Phil
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Re: Do It Yourself: 240v from two 120v sources

Tue Jun 14, 2011 3:35 am

Thank you sir; I liked the idea of being able to hear it without having to look at anything... Off to the lab I go!
Ingineer wrote:Ok, I added the Buzzer:
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Re: Do It Yourself: 240v from two 120v sources

Tue Jun 14, 2011 8:25 am

ggodman wrote:Nice... thanks!
Yes. Thanks, indeed. I especially like the clean symmetry of the schematic drawing. Time to source the parts.

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Re: Do It Yourself: 240v from two 120v sources

Tue Jun 14, 2011 8:49 am

Can someone elaborate on why you'd want the 120v switch? I must be missing something. Seems to me if you want 120v, just don't use this device at all... ;)

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Re: Do It Yourself: 240v from two 120v sources

Tue Jun 14, 2011 10:14 am

OK, my trip to the junk boxes resulted in some components that I used to build a slightly different version. The relay logic and wiring is the same as the schematic (I didn't use the 120/240 switch). However, I went with a different type of noise maker and light based on what I found.

I have an old 240VAC Sonalert that is a momentary type (it sounds for 5 second than goes off when power is applied) and I used that by wiring it directly across the 240 output through two 10 ohm 1 watt fusible resistors (one on each side of the Sonalert) for short protection.

Across the Sonalert I wired a 240 volt Neon cartridge indicator that I also had in parallel. Testing showed that the Sonalert wouldn't trigger on 120 but would on 240 so it was perfect for this. Likewise, the light is very dim on 120 but quite bright on 240.

Not as elegant but having all the parts available in the shop was a plus.
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Re: Do It Yourself: 240v from two 120v sources

Tue Jun 14, 2011 10:21 am

I will seriously pay someone $5 to make this for me :lol:

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