5v and 24v Power Supply

[Joshua]

Hey everybody. For my latest project, I require both a 24 VDC and a 5 VDC power supply. They do not need to have common ground; a configuration of +5V, +12V, -12V, and GND would be acceptable. The 24V supply needs to be able to supply about 1A as it will only be used to power 3 solenoid valves at about 250mA each. I think 1A would be sufficient for this, but if anybody disagrees, let me know. The 5v supply will be used just to power a micro, lcd, a couple LEDs, EEPROM,etc... so I think a 500mA supply would be sufficient there.


My question is, what would the group recommend as the best option for something like this? I don't want to take the time to custom design a dc/dc converter for this, but am open to using an off-the-shelf one. Some of the thoughts I had was to use a 24V CT transformer. Then I could use either a lm317 or lm7812 and their negative counterparts to get +12 and -12 for my 24V. I could then put a 7805 on the 12v line to get 5v. I am open to using a heatsink, but I want to avoid the need of having a fan.


Another option is I could get a 24v transformer and use a lm7824 or a lm317 to regulate to +24v and use something like this
http://www.mouser.com/Search/ProductDetail.aspx?R=R-78E5.0-0.5virtualkey56830000virtualkey919-R-78E5.0-0.5
to get 5v.


Are either of these options viable, or is there something I've overlooked?


Thanks.
Joshua

[SeanB]

24V industrial power supply in a DIN mounting case and the 24-5V switching regulator.

Otherwise look up arcade machine power supplies, these give 5V and +-12V rails with reasonable regulation on the 12V rails but good regulation on the 5V rails. Often adjustable from 4-6V and the 12v from 10-15V, and each of the 12V rails can do 1A and the 5V supply can do 5A. Sef contained in a metal module that just needs mounting. Some even have the required 24V and 5V rails you want as standard.

I have a few of these that are quick and dirty power units for checking, they came from dead arcade machines.

[lewis]

The 24V supply probably doesn't need to be regulated if it's just driving solenoids, an 18V transformer will give you about 24V once rectified and smoothed. Then, just simply connect a 7805 to the unregulated 24V line for your regulated 5V.