30-25 volt converter ic other than 7805

[ashwinraj]

is there any ic that will convert 30 volt to 5 volt other than 7805, reverse operation ulm2804 to interface 8 i/p of 89c51
also please suggest me a good transistor switch that will convert 30 volt to 5 volt to interface 89c51


rajashwin88@rediffmail.com

 

[kripacharya]

7805 is not exactly a voltage converter.

what are you actually trying to do ? Just interfacing a 30v switching signal to uC input pins ? If so, wouldn't a simple resistive divider + zener protection be enough ?

 

[Tahmid]

For "converting" voltages as high as 30V to 5V, to be used for power sources, you could use switching regulators instead of 7805 to maximize efficiency and minimize power loss and heat. There are many such switching regulators available. You may take a look at L4971 and LM2575 among others.

L4971: https://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001355.pdf
LM2575: www.ti.com/lit/ds/symlink/lm1575.pdf

Hope this helps.
Tahmid.

 

[ashwinraj]

please see my circuit diagram, i want to convert 8 sensor o/p voltage (voltage range 5 to 30) to 5 volt to interface 8 pins of microcontroller 89c51View attachment UC.bmp
also in circuit diagram i used a not gate at o/p of all transistor
AND+RC+NOT is for positive edge trigger, is it possible clear an input pin in uc89c51 programtically once the pin is declared as input.
i want to replace all transistor circuit with an ic
also suggest me proper transistor switch circuit to interface uc89c51

 

[kripacharya]

edge trigger is usually a term used for interrupts. Are your uC pins capable of accepting external edge-detect interrupts ?
If so, then just do the settings for edge detect, and throw away all your external circuits.

If not, then you have to poll / read the pins regularly and fast enough to see if they have gone active, and then take appropriate action. Then wait/ check for that pin to go inactive and active again before the next action.

Thats it.

To translate from 30v to 5v, you just need a resistive divi.... oh i already wrote that in post #2

 

[ashwinraj]

i want to convert i/p voltage range 6 to 30 voltage into constant 5volt

 

[per_lube]

i want to convert i/p voltage range 6 to 30 voltage into constant 5volt

Use LM317 with a suitable resistor values. There's a nice online tool for calculating resistor values for LM317 here : http://www.reuk.co.uk/LM317-Voltage-Calculator.htm
The regulator has a voltage drop of ~2V across the chip. Therefore it'll regulate the range ~7-30 V into 5V.

The maximum current it can provide is 1.5 A and when drawing currents more than 300 mA, a good heat sink is recommended