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Electronics => Electronics => Topic started by: dsesmg on August 19, 2009, 03:20:24 AM

Title: Converting 24VDC into 5VDC
Post by: dsesmg on August 19, 2009, 03:20:24 AM
Hi, I am trying to learn how to convert 24VDC into 5VDC.
There must be many ways to do this.
I hope I could learn the most cheapest yet reliable way.
Please help.
Thank you!
Title: Re: Converting 24VDC into 5VDC
Post by: SmAsH on August 19, 2009, 03:28:37 AM
a voltage regulator ic.
most normal ones will do, a 7805 with a heatsink should suffice.
if efficiency is really required, a switching regulator should be used.
Title: Re: Converting 24VDC into 5VDC
Post by: billhowl on August 19, 2009, 04:06:35 AM
If you need low cost switching regulator then try this

Consider discreet circuits like  "The Black Regulator" Input: 10v to 18v output +5V, +12v 70mA to 300mA
http://www.romanblack.com/smps/smps.htm (http://www.romanblack.com/smps/smps.htm)

The input voltage can go higher by changing some parts in the circuit.

for other switching regulator type read here
http://www.societyofrobots.com/robotforum/index.php?topic=8794.msg68534#msg68534 (http://www.societyofrobots.com/robotforum/index.php?topic=8794.msg68534#msg68534)
Title: Re: Converting 24VDC into 5VDC
Post by: dual on August 19, 2009, 12:01:00 PM
If you're very specific about converting a 24V to 5V, I looked into DigiKey to find the right part for you.

The part that would be perfect for you that's in stock at DigiKey right now is called BA05CC0T-ND. Just look for that in the search box in Digikey.

And for your information, I will tell you the steps I did to find this part:

1.) go to digikey.com
2.) search for Voltage regulator in the search box
3.) there will be a bunch of categories but you need to look under Integrated Circuits and click Voltage Regulator - Linear
4.) there will be a table that you can use for filtering and what I did was towards the right, under the column Voltage Output, look for "5V", click it and then click Apply filter on the screen to the bottom left.
5.) the filter table will be reduced and then under the column Voltage Input, look for a range that has your input voltage requirement, in your case 24V. I clicked on 4~25V and then click Apply Filter again.
6.) the search result should be narrowed down pretty well and just look for one that looks the simplest, and of course in Stock. In this case, I chose the one that has the least number of pins.

There ya go, hope that helps.
Title: Re: Converting 24VDC into 5VDC
Post by: benji on August 19, 2009, 03:40:31 PM
just be sure that the 7805 can bear with 24 volts as input, not sure of that.
plus its not efficient to use this IC.

the best is to use a transformer with a rectifier or a switching dc-dc converter
Title: Re: Converting 24VDC into 5VDC
Post by: SmAsH on August 19, 2009, 03:55:22 PM
the datasheet says the 7805 can take a maximum input voltage of 35-40v... wow, thats heaps of wasted energy!
Title: Re: Converting 24VDC into 5VDC
Post by: billhowl on August 20, 2009, 02:46:20 AM
I had found this 3-Terminal 5V 1A Switching Voltage Regulator operates over a wide range of input voltage up to 40V, it cost USD $8.99 or $80.91 if you buy 10
http://store.gravitech.us/35v1aswvore.html (http://store.gravitech.us/35v1aswvore.html)
(http://gravitech.us/MicroResearch/PowerSupplies/SWITCHING-3TERM-5V/SWITCHING-3TERM-5V_8.jpg)
Title: Re: Converting 24VDC into 5VDC
Post by: dsesmg on August 21, 2009, 07:28:14 AM
Hi, thanks a lot.
As a matter of fact, I rather intend to build my own converter.
If you need low cost switching regulator then try this

Consider discreet circuits like  "The Black Regulator" Input: 10v to 18v output +5V, +12v 70mA to 300mA
http://www.romanblack.com/smps/smps.htm (http://www.romanblack.com/smps/smps.htm)

The input voltage can go higher by changing some parts in the circuit.
Could you be more specific about the parts that are need to be changed to increase the input voltage?
I have a 24V, 15A power supply at the moment, and I am going to convert the voltage of this power supply into 5V.
Title: Re: Converting 24VDC into 5VDC
Post by: billhowl on August 21, 2009, 09:57:28 PM
The change is listed inside the articles
Quote
High voltage use

I have had some inquiries re using the Black regulator for high voltages, ie 40v up to maybe 120v or so. High voltage input is one area where this circuit can really beat the dedicated smps chips (or 78xx regulator chips) as these chips rarely accept input voltages over 30v or 40v.

If you want to use the Black regulator for high voltage circuits I suggest the following:
 Make sure Vce of Q1 and Q2 is rated 50% higher than input voltage
 Use a darlington for Q1, so you can use a high value resistor for R2 to keep R2 dissipation low
 D1 must be Vr rated at 50% higher than input voltage, a schottky probably won't do. Try a 1N4937; 600v 1A fast switching diode
 Increase RZ resistance
 Reduce C1 and C2 as RZ was increased
 A resistor in series with C2 may be needed
 Retuning of the C1:C2 ratio will be needed, use a much smaller C2
 R2 and RZ may need to be 0.5w or 1w types - check heat
 Use a fuse on circuit input!
Title: Re: Converting 24VDC into 5VDC
Post by: Truckstop on August 22, 2009, 01:23:47 AM
It really depends on how many amps you want to pull through the 5V regulator

Truckstop
Title: Re: Converting 24VDC into 5VDC
Post by: Soeren on August 22, 2009, 09:22:24 PM
Hi,

the datasheet says the 7805 can take a maximum input voltage of 35-40v... wow, thats heaps of wasted energy!
No it can't!
Some datasheets lists the 7805 to have an Absolute Maximum input voltage of 35V (not 40V!).
To quote from a datasheet:
"Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is not implied."
An 7805 is considered to have a max. working voltage of 24V (which is still a lot of power wasted).

Try this switch mode equivalent of the 7805 http://www.dimensionengineering.com/DE-SW050.htm (http://www.dimensionengineering.com/DE-SW050.htm) for a relatively loss-less (<1.5W worst case) regulator with a working range input of up to 30V (use it just like the 7805, it's a monolithic regulator).