Connecting AC/AC 9v adaptor to breadboard

Hi all,

A couple weeks ago in my Circuits II class, we learned about full wave bridge rectifiers for converting AC to DC voltages, linear regulators, and capacitance to output a 5v DC. I wanted to take this a step further and try to breadboard this on my own(we did our lab using LTSpice), and eventually getting a stable 5v out for me to buy a usb connector (something like this), and have it charge my phone. I thought it would be a fun little weekend project, but have gotten caught up with class.

My original plan(which was very dumb), was to connect a transformer to mains. I know, if you're reading this, don't do it. I caught myself quick. Instead, I purchased an AC/AC to 9v wall plug and it has a little cylindrical end that would be able to attach, but I cannot seem to find any plugs that can go into my breadboard that would take 9v AC. Everything I have found is 5v DC only (like this). My plan is now to find a way to connect my 9v AC power source into my breadboard, wire up a full wave bridge rectifier, and try to get myself a stable 5v output. I still have to figure out all of the math to get it all working correctly and safely for my phone, but that'll only take around an hour or two to dig through my notes.

My questions are: How would I go about connecting my 9v AC to my breadboard? Can I just cut the tips off and get exposed wire? I have very limited breadboarding experience as much of experience in the past two circuit classes have been through LTSpice, and rarely any breadboarding.

Thanks.

Hi,

Why do you want 9V AC?
5V DC adapters are way more common and usually cheaper, too.

Klaus

KlausST said:

Hi,

Why do you want 9V AC?
5V DC adapters are way more common and usually cheaper, too.

Klaus

Click to expand...

Well, the goal was to practice my breadboard skills and learn a bit in the process. I wanted to breadboard the whole rectifier myself. I already bought the necessary diodes, capacitors, and linear regulator to attempt to rectify my 9V input AC to a usable 5V DC so I can try charging my phone.

Hi,

I understand.
My personal opinion: It may give some basic skills, maths, capacitor calculations and so on.
But it´s not modern design of power supplies. Rather 1970ies style.
With it´s drawbacks like: heavy, big, expensive, low efficiency = dissipated power = heat..
It may have it´s benefits, too.

***For your breadboard:
There will be connectors, screw clamps, spring clamps... that can be placed on your breadboard. I´d cut of the connector of the 9V AC wall wart and use the bare wires..

***Breadboard in general:
There are many nowadays circuits that are not suitable to be tested on a breadboard. HF design, high speed switching signals, switching power signals, low noise....
So if your breadbaord circuit fails ... it may work on a true PCB.
Don´t expect too much from a breadboard test.

Klaus

KlausST said:

Hi,

I understand.
My personal opinion: It may give some basic skills, maths, capacitor calculations and so on.
But it´s not modern design of power supplies. Rather 1970ies style.
With it´s drawbacks like: heavy, big, expensive, low efficiency = dissipated power = heat..
It may have it´s benefits, too.

***For your breadboard:
There will be connectors, screw clamps, spring clamps... that can be placed on your breadboard. I´d cut of the connector of the 9V AC wall wart and use the bare wires..

***Breadboard in general:
There are many nowadays circuits that are not suitable to be tested on a breadboard. HF design, high speed switching signals, switching power signals, low noise....
So if your breadbaord circuit fails ... it may work on a true PCB.
Don´t expect too much from a breadboard test.

Klaus

Click to expand...

Hmm, thats interesting. Thanks for the insight!

theonetrue2 said:

Well, the goal was to practice my breadboard skills and learn a bit in the process. I wanted to breadboard the whole rectifier myself. I already bought the necessary diodes, capacitors, and linear regulator to attempt to rectify my 9V input AC to a usable 5V DC so I can try charging my phone.

Click to expand...

Are you sure the output is 9Vac and not 9Vdc?

What diodes, capacitors, and regulator did you buy?

crutschow said:

Are you sure the output is 9Vac and not 9Vdc?

What diodes, capacitors, and regulator did you buy?

Click to expand...

Yes, output 9Vac.
For diodes, 1n4001.
Capacitors, 1uF and 0.1uF. I haven't calculated how much the smoothing capacitor should be yet.
Linear regulator, LM7805.

I haven't been able to think too much about this whole thing since I've been so busy with school, so any suggestions are greatly appreciated!

theonetrue2 said:

My original plan(which was very dumb), was to connect a transformer to mains. I know, if you're reading this, don't do it. I caught myself quick. Instead, I purchased an AC/AC to 9v wall plug ...

Click to expand...

Most wall plugs that have AC/AC in/out have a transformer built in. If the 9V output is AC, I do not see any difference with a regular transformer and the wall plug.

However, most of the wall plugs AC/DC type have a SMPS built in and the DC output has good regulation. If you want a high power unit (>1A or about 10W power) then the circuit cannot be accommodated in the body of the wall plug (or it is a big brick).

These linear regulators are very good for local regulation and low power demands. Most phone chargers these days can deliver more than 1A (most deliver 2A) and some can go upto 3A.

But yes, you can cut off the connector and use the bare wires.

c_mitra said:

Most wall plugs that have AC/AC in/out have a transformer built in. If the 9V output is AC, I do not see any difference with a regular transformer and the wall plug.

However, most of the wall plugs AC/DC type have a SMPS built in and the DC output has good regulation. If you want a high power unit (>1A or about 10W power) then the circuit cannot be accommodated in the body of the wall plug (or it is a big brick).

These linear regulators are very good for local regulation and low power demands. Most phone chargers these days can deliver more than 1A (most deliver 2A) and some can go upto 3A.

But yes, you can cut off the connector and use the bare wires.

Click to expand...

I agree, configuring a transformer would be the same as wall plug, but I'm sure that playing around with mains power can be lethal especially if I'm a noob.

Take note of c_mitra's comment about the current drawn by some phones when on charge. The LM7805 is rated at 1A when at room temperature but it has to be de-rated to lower current at higher temperature. That means you will almost certainly need a heat sink to keep it cool. Without one, you run the risk of it either shutting down or melting your breadboard, whichever happens soonest!

Brian.

theonetrue2 said:

I agree, configuring a transformer would be the same as wall plug, but I'm sure that playing around with mains power can be lethal especially if I'm a noob.

Click to expand...

Safety always comes first. Like they say, fire is a good servant but a bad master. So is high voltage.

High voltage can be dangerous but many of the electronic components are ESD sensitive and you need to be careful there too. You need to take care of yourself first and also take care of the circuit next.

By the way, 9V after rectification and filtering will be close to 12V and the regulator will dissipate about (12-5)x1=7W (theoretically)

I doubt you will be able to get 1A continuous output using the setup.

c_mitra said:

9V after rectification and filtering will be close to 12V

Click to expand...

I guess even more.
Small transformers are weak, especially when they are "short circuit proof".
Now the 9V RMS is usually rated at full load, so at low load .. maybe there is 12 V RMS, making more than 15V at the regulator input.

Klaus

Hi,

The word 'fuse' is sadly missing from this thread.

Hi,

Are you familiar with the concept of derating?

I'm not very expert, someone else can fine tune or correct my suggestions, but if you wish to continue with the project, and can splurge on far more adequate components, I would recommend:

Really important: fuseholders and ...maybe 2A to 3A fast fuses
(one at input of breadboard, but bear in mind that breadboards aren't really appropriate for a mobile phone's current draw).
Accidents/Mistakes can happen, that's life and prototyping, and better to blow one fuse than wreck several components.

A 9V, 5A regulator
(to share large voltage drop and thus PD before the 5V regulator, might help save on heatsink sizes and costs)

A 5V, 5A regulator (to follow 9V regulator still 4V x phone charger current = [Vin - Vout] x Iout of PD)

e.g. 1N5400 rectifier diodes for the bridge. 1N4001 is a bit small for a phone charger circuit, IMO.

Consider smoothing capacitor is a world of its own, too, before buying anything and getting buyer's remorse by making a mistake - we all do that at first. Electrolytic capacitor capacitance is supply voltage (and temperature) dependent... 1,000 uF by name will be far less in-circuit (read the datasheet before buying and see relevant graph). Derate by selecting a 35V or so capacitor and read up a tiny bit on permissible ripple current (you don't have to become an expert, just understand the parameter and concept a bit).

Might want to consider a suitable wattage resistor as a dummy load for the moments nothing is connected, as KlausST said - might be 15V AC with no load.

A couple of strategically-placed LEDs (and their respective current-limiting resistors) are useful to see if all is well or not before needing to get the DMM out... Visual indicators.

Presumably, you'll need heatsink(s) and may want to add a fan.

Don't be a dozy newbie like I used to be, there is an order to shopping then making:
Read up on topic/project > do relevant sums > ascertain component needs > browse datasheets > do relevant sums to see if prospective components are actually an adequate choice > click on 'buy now' > make circuit carefully > be happy with achievement.

There may be other stuff but can't think of much else right now.

Good luck and enjoy it.