about a transformer

Hi .
It is possible to connect the two 12 transformers in parallel this would give you 12 Ac and approx 1.5 amp. Altough i would not advise such connection. The other thing you need to check is the maximum voltage the amplifier will tolerate. After rectification and smoothing with no load a 12 Ac transformer will give you approx 15.5 Vdc can your amplifier deal with this much voltage. also you will need to take into account mains voltage variations and also the regulation of the transformer you use... IMHO i would source a transformer with the right specification in the first place..

Regards Ian

Assuming that by "transformer", you actually mean a mains-to-12-Volt Power Supply Unit, connecting them if parallel is possible, to give you 750mA x 2 = 1500mA = 1.5A

(Ensure correct polarity, [+ to +] and [- to -], or they will blow each other up.)

It is preferable if they are identical units so the output voltages will be exactly equal.

It is better to describe these units as "PSUs", Power Supply Units, to avoid confusion,

SO, like the man says, you need to buy a mains-to-12-Volt PSU of (minimum) 2 Amps output.

Or tell your teacher, from me, to give you a project that is powered by what you have, or supply you with the PSU.
(Because there is absolutely no need for a school educational electronics project to be that powerful !)
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(If by "transformer" you mean an actual transformer (mass of thin steel plates with wire windings), and if they are identical, (once again they must be connected "in phase"), it is still only possible to get 1.5A, but it requires a rectifier circuit for a DC powered amplifier. But even then I don't think your teacher wants you to be experimenting with mains voltage connections of equipment unless under direct supervision of a qualified electrician or similar.)

I would do it as shown in the attachment. BUT, two 12V 750ma transformers will only supply a max of 1.5 Amp and your spec is 2 Amp, so it may not be enough. But, then, unless this is a Class A audio amp, that is merely a peak demand, so just keep the volume down ;)

Also, the rectifiers will reduce the output voltage by around 1.4 Volts.

Also, you will probably want to put a regulator on that, which will knock the output voltage down yet more (by as much as the drop-out voltage of the regulator, so use an LDO).

If the transformers are exactly the same, you might get away with connecting the primaries directly in parallel. Theoretically the output voltage will be the same and the current capacity will double.

Apart from what other people have mentioned why not got to a rubbish dump pick off the old HI FI units and I guarantee you will find a 12/ 24 volt tx that is suitable

The other day I needed some relays I picked up a discarded alarm system and hey presto on the PCB which the MNFR had varnished so as to make this unserviceable which it never was in the first place

So with a bit of patience and 20 minutes hard work Guess what a small blowtorch and bingo I salvaged 8 of those relays That’s a grand saving of £32.34 pence

Just shows you just how much money these big boys waste , also proves that there is plenty of money in recycling components even Transformers So if you are stuck contact me and Il even send you a TX that you want with a good current rating at an affordable cost plus P& P

Don’t believe me here is what I picked up and the cost if I had have gone to Maplins or Farnels Or RS components

http://mercury.maplin.co.uk/catalogue/ebook.html?page=866 Go check this out yourselves

A simple lesson in Recycling making things re usable at a depreciated cost that’s even beaten the big boys

Ill prove this to you every single time even i learnt something from the chinese and the likes of Lord Alan sugar

MD Harrington
www.harrington.force9.co.uk

Yes they all say its a throw away

Wrong !!! "That’s what they want you to think " Don’t be wasteful be resourceful

hello again sir: thank you all for those informative response.. I have here the diagram, I made that lay-out with those specs because for now that's the only transformer I have, I have no other means. so when I get the proper transformer I would definitely recreate it. please correct whatever mistake you will find in this diagram. thank you very much I deeply appreciate all of your help.

hello sir,, I need help and clarification about our school project.. an audio amplifier that is supplied with 12volts 2amp .. the problem is , I don't have that kind of power supply.. what i only have is two 12volts 750ma transformers ..i would like to make a lay-out.. the question is here.. is it possible to combine two 12volts 750ma in one circuit ?? is the output would still be 12volts?? what about the ampere??? thanks for helping
hello again sir: thank you all for those informative response.. I have here the diagram, I made that lay-out with those specs because for now that’s the only transformer I have, I have no other means. so when I get the proper transformer I would definitely recreate it. please correct whatever mistake you will find in this diagram. thank you very much I deeply appreciate all of your help.

diagram

Would we correct the diagram for him ??? Hmmm what diagram?? and would we please design this for him as well so that he can obtain an A for his subject at school whilst all the rest of the students obtain lower mark than he does

Yes Ok say no more

Would we also walk out look at the bins outside the homes of various residents and would we also find him a transformer which he can also do for nothing himself because he’s

a little short of cash What have I just put in here for his benefit I’ve even told him how to obtain one and where from I don’t know you tell me and this is supposedly a country that is resourceful where we are frequently told and shown in TV programs how poor they are which yes I see and what they have to do to obtain money I watched this too on TV in the UK and I thought what a clever idea “ Go to the rubbish dumps look at what people throw away and re manufacture

How is it that I saw sense yet this person cant “It does make you wonder does it not !!”

In fact it reminds me of the news I saw tonight regards thge petrol crisis "Ill leave you to think on this too with modern technologies such as the smart phone , Ipad , cloud , Free Open source , networking , two way radio communications , The net , laptops , RF technologies , wifi , Bluetooth etcetera , Whilst the roads jam up outside the petrol stations because they still cant use modern day communications

Hmmm I know too with the Truck driver complaining about how hard he has to work for his 47K salary a year "Poor person you "

Mark

www.harrington.force9.co.uk

We live in hope I guess