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Author Topic: 8v2a to 16v1a  (Read 832 times)
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I have a transformer that puts out 8v2a, I want to make it put out 16v, from what i understand (limited) this is possible, but how would you do it.
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I have a door bell that i built, it has 4 mechanical ringers, hence the 8v,2a transformer, but 2 of the bells wont ring because they are to far away and the power drops off to much, so i figured, if i used the arduino, i could.
A, ring the bell for as long as i wanted off one bell push.
B, Only ring one bell at a time thus giving maximum power to each dome/bell.
C, Increase the voltage for the far away bells so that they will actually sound

At the moment i have the arduino set up to cycle through all four bells on 12v dc power, all is well, but i know that when i put it onto the wire that is 25mX2 long, 12v most likly wont be enough.

At the moment I have a 1.5v-12v wall wart that i am using, but i have the transformer that i bought for the bell, which is 8v2a, and i think it might be ac, a rectifier is no problem i believe.

The other thing thats quite cool about using the arduino as a door bell is that i could put an lcd on it and have it say somthing when someone pushes the bell.
EG, not in at the moment, leave any parcels at no 10's, or ring this number, if ur a sales man, piss off. lol.
Obviously you use a switch to change th emessages easily, or a key pad. what ever, for now, I just want the damn bell to ring when i am at the bottom of my garden, which is often as my workshop is there.

Cost wise, the arduino is actually quite a cheap way of getting a complex customised door bell working.
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You need a "Bridge circuit", if transformer has only one 8V secondary windings:
http://en.wikipedia.org/wiki/Voltage_doubler
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thank you, so if i was to use the Greinacher circuit, the transformer being 8v2a ac, what capacitors should i use, i dont know how to calculate it, i have some 220uf 16v + 470uf 16v, are any of them any good?
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470x16V should be o'k, it's not clear how much current your bell consume.
Bridge circuit, I don't think Greinacher is good with electrolytic caps. 


* 200px-Bridge_voltage_doubler.svg.png (5.66 KB, 200x95 - viewed 22 times.)
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Hopfully image will attach, so if i laid it out on a bread board like the pic, that would work?. Bells use 8v, but i have seen them ding on about 6v. The voltage has to go a long way, total 50m round trip, so there is a lot of drop off, to much voltage is no problem i believe, but to little and nothing will happen. I will only ding one bell at a time, obviously, i will only double it for the bells that are far away.
in the drawing, (dont fully understand them) which way is + on the capacitor, I am assuming the top is + (the long wire).

When you said, current, do you mean amps, I think its 8v1a, because the transformer to run one is that, and to run 2, its 8v,2a.


* bridge_bb.jpg (41 KB, 817x588 - viewed 22 times.)
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Why not just add a local power source at the end of the 25m, and only send a control signal over to manipulate the 8 or 12V at the far end?
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This is my current layout, but it has 4 bells, this layout only shows 2, it works just fine, as i understand it, the 25m would lose a small 5v signal. it lost the 8v, all i was getting at the other end was about 1v. I would like to try to keep it all running under 1 power suply if i can.

The fets are actually tip120 transistors.
and the speakers are obviously the bells.


* bell 2_bb.jpg (59.6 KB, 1120x729 - viewed 23 times.)
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Well, I messed arround some more,  I boosted it to 24 volts, and still I only got 2v at the other end?, then I tried CrossRoads sugestion and lo and behold the signal got through, so I am going to have to do it that way. Thank you CrossRoads. I actaully used the tip120 as a relay, it works just fine.
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Quote
The voltage has to go a long way, total 50m round trip, so there is a lot of drop off, to much voltage is no problem i believe, but to little and nothing will happen

So you want a maximum of 2V drop out at 2A over 50m?  Then you simply need wire with a resistance of less than 0.02 Ohm/metre, which means copper wire of cross sectional area 0.7mm^2 or more, problem solved - usually the cheapest cable is mains cable BTW.
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