voltage divider for DC to DC converter ?

we purchased a massage chair from china , shipped to my home . my sister -guided by the label on the

chair - plugged it in 220v AC but the chair did not work, plugging it in 110v AC did not work either.

being the home electronic "pro" ( lolz i don't know any real shit about electronics) i was asked to look

into it.i decided that it will be a good learning tool ( lolz) .

upon opening the chair i found that the ac/dv transformer was labeled "110v" so i thought that plugging

it into 220v broke it. i found the fuse to be burned.

replacing the fuse did not help. chicking the dc output of the transformer i found that it is faulty.

the tranformer is labeled as such:
110v AC input

20v DC output 1 amp
12v DC output 3.5 amp

yes it has 2 output plugs. so i decided that i will buy another one. but searching the local market i

only found 220v AC input , 24v DC output.220v AC input is nice for out area ,but 24V will not do any

good.

my solution is : just use voltage devidor to convert 24 volt to 20. and use the same idea to convert 24

volt to 12. job done.

right or wrong ?
will the cost of resistors be acceptable ?

Hi,
Having a resistor divider will spoil your transformer's output impedance and it would change the output voltage depending on the load current. If your load (circuit board or motor?) cannot take the 24V then without the right transformer converting the 24V to 20V and 12V with the given current ratings will be very complex.

I too agree with aryajur.... voltage divider output will change when you load current changes........... so it is better to find a transformer.......... Another way is that find two transformers one having a value of each output...........

Now if the above are not applicable......... Use the VOLTAGE REGULATOR ICs.......

for 20V dc 1A you can use 7820 regulator..... with heat sink 7820T - 7820 20V 1A Positive Regulator
for 12V dc 3.5A either you can use high current voltage regulator (LM338- Adjustable) or a normal regulator like lm7812 in conjunction with power transistor to boos up the current..... with heat sink........ check thread https://www.edaboard.com/threads/77041/

thank you
we had problem finding 20v power supply. i figured out that the power supply of some laptops are 20v.
cheers