help regulating voltage

Google "buck converter".

thx, i did a fast search, do i need to know the exact amount of current of the load?

What is the LM317 doing? What voltage is coming in to that bridge rectifier attached to the LM317?

the lm317 is the one supplying 24v, this is becuase I need 24 v for a sensor

do i need to know the exact amount of current of the load

You don't need to know the "exact" amount, but you should not draw more than the regulator is rated at. Better safe than sorry..

If im good at my estimates, i am not drawing more than .5A so i think i could design a 1a regulator, so i am trying to figure out how :slight_smile:

input is 24v
ouput is 5v
iOutput 1a

You could use two of something like this, one for 5V and the other for 3.3v

That's a lot of current.Look at pololu.com for step down regulators.

well i dont know hwo much current i am actually consuming, my sensor peak current is 70ma and the arduino takes about 100ma the nrf24l01 is about 40ma? im not sure

That's a lot of current.Look at pololu.com for step down regulators.

what does that mean. He requires a lot of current? What URL are you suggesting? Please put in a hyperlink tag. Did you find one that is less expensive (include shipping). Please give us the URL. Thanks

hey jack, could you help me design a buck converter under those specs? would it be cheap?

i found this MC34063A switchable regulator on a shop, but i just dont know how to wire it.

You don't give us a URL?

The example I presented to you cost $3.80. Do you find one less expensive. What's the URL ?

i am not buying it from here, a local store sells for $2.90, but i belive i need extra components

I don't know anything about that IC. I would suggest spend a dollar more, and get all the components on the board.

can you help me on how do i need to design it?

If you have a dollar store near you, see if they have any cigarette lighter plug to USB charger adapters. You are nearly 100% guaranteed that it'll have a MC34063A buck regulator in there. Complete with schottky diode and coil.

Many of the cigarette lighter plug phone chargers also use the MC34063A chip.

The Dollar Tree here has them now and again, and the ones they sell use a rewindable inductor and the chip itself, the diode, and inductor are through-hole components. You'll have to replace the input caps to withstand 24V (use 35V capacitors) and change some other components.

There are Javascript calculators on several websites, I like this one because it automatically selects buck or boost, and you can use a percent variation of input voltage to account for changing supply voltage:
http://dics.voicecontrol.ro/tutorials/mc34063/

This chip has a built-in current limiter, it can output a maximum of 750mA. However! You should not be daisy chaining regulators. The LM317 in your circuit, besides having insufficient input smoothing capacitance, has to carry all the circuit current. You never said, what is the input voltage there? Is it AC, or is the bridge rectifier there just so it doesn't matter which way a battery is connected? Either way, there should be more capacitance there.

The MC34063 can withstand up to 40V of input voltage.

if i use that calculator i get this

Vin = 24.00 ±10% V
Vout = 5.00 V
Iout = 500.00 A
Vripple = 0.10 V

Vin min = 21.60 V
Ton / Toff = 0.34
Ton + Toff = 10.00 µs (micro seconds)
Toff = 7.49 µs (micro seconds)
Ton = 2.51 µs (micro seconds)
Ct = 100.47 pF
Ipk = 1,000.00 A
Rsc = 0.00 ?
Lmin = 0.04 µH
Co = 12,500.00 µF
R1 = 10.00 k?
R2 = ((Vout - 1.25) / 1.25) * R1 = 30.00 k?

isnt 12,500uf a bit unrealistic?

i cant afford the time that would take me to get those here