My Power Project

I am sophomore doing a project on Auto Voltage Selector. My project works such that depending on what voltage the load requires (110 or 240), the supply automatically switches to the required voltage.
I do this by using 2 different comparators that takes and only one of them is on at a time which triggers one of the triacs at a time.
I got info and help for this project from this website below.
**broken link removed**
The problem is that I couldnt find the lat part required for the project that is the switching transformer and I don't have the time to wait for it.
My colleagues suggest we use a switch ckt instead for the demo purposes whereby one switch wuld trigger 110 volt and other switch wuld trigger 220 volt.
I understand that voltages in series add up and I used that technique to make the switching ckt but end up getting the same 110 volt at the finla output.
This is the scenario
A-----(Live Wire from Primary Winding)
B-----(One of the selectors)
C-----(The Second Selector)
I am getting 110 V between A - B and 110 V between A-C. So since they share the common node, when I connect them in series, I dont get the 220 V I need.
Any advises on how I can complete the project.

Voltages in series dont aways add together. I dont think this is your problem but be aware when working with multi-coiled secondaries that polarity of the coil determines if it adds or subtracts from the other. Coils will normally be marked with polarity dots, depending on how you connect the coils you can either add them together or have them subtractive.

The problem is, that the coils are not connected in series. There is no way you could connect two transformers or two windings of the same transformer and get the voltages you think you have. Unless there are two transformers and one of them is not powered.

Power Project

thanks so much for your response
the thing is that there is no way i can arrange for a siwtching transformer used at the end of the ckt. is there any other alternate i can use for the sake of demonstration?
also, i am having a feeling now that i misunderstand the way the peoject works. if anyone can break it down to me how the ckt is supposed to be working, that can improve my understanding onit.

**broken link removed**

The LM339 circuit is a window comparator. When the voltage from the control transformer is higher than the 1N4735 zener voltage, the lower triac is turned on thru the MOC3022 opto coupler which applies the input power to the center-tap of the transformer (this is wrong, the other triac should be the one turned on). When the voltage from the control transformer is less than the voltage of the 1n4735 zener, the upper triac is turned on which puts the input power to the whole primary of the transformer. If the outputs of the window comparator are swapped, this circuit should work.