24v - 5v supply

[justwhy2003 0]

Hello My PLC uses a 24 volt supply but the transducer i am using as a input requires a 5 volt supply. For testing purposes i have just been using a 5 volt regulator to produce the 5 volts but will this seffice for the application when applied to the process. My question is, how appropriate is it to use the 5 volt regulator? In more experienced opinions is this suitable or should I use a seperate 5 volt supply. Thanks Justwhy2003

[rpraveenkum 5]

It is better to have seperate 5V source

[BobLfoot 302]

A seperate 5V supply will cost more in terms of parts and materials, but will be fewer headaches on the maintenance side and they usually dress out enater than an LM 317 and soldered wires.

[Ken Moore 23]

Use a dedicated 5VDC supply. That way many years down the road, when all the documentation is lost, and a maint. person is tracing the wires, he/she will follow it to the power supply and know that it is 5 volts.

[TConnolly 13]

You could also use a DC/DC converter such as one of these: http://www.sola-hevi-duty.com/products/pow...es/pdfs/scd.pdf Farnell carries them on your side of the pond. http://ie.farnell.com/jsp/Electrical/Power...jsp?sku=1159454

[justwhy2003 0]

Is maintenance the only draw back? Would a 5 volt regulator detereriate over a short period of time? I cant find a cheap power supply with dual 24 volt/5volt output. Justwhy2003

[Clay B. 1]

I tend to shy away from dual power suplies all together for 2 main reasons: price and availablity. 5vdc pwoer supplies can be had quickly and cheaply from almost any electrical supply same with 24 vdc. Also since it is 2 seperate power supplies you can islote them from each other if noise becomes an issue on 5vdc. Example would be you had 24vdc solenoids. Firing these can cause noise. Instead of having to filter the noise at the solenoid you can isolate the 5 vdc power supply and everyone is happy.

[panic mode 246]

i agree on separate PSU... you need to provide more information, for example what kind of budget you think of, any space constrains, how much current you expect to draw from this 5V power source etc. standard DIN-rail mountable power supplies like IDEC PS5R-A5 or B5 are only some 35CAD or about 16GBP but there are regulated wall-plug style power supplies for barcode scanners etc for less than half of that. when using standard regulators, key is to keep the temperature low so if you only need few mA you can use any standard regulator and it will last forever. most of them have thermal overload built in. for example simple positive analog regulator with 10mA regulator current and 150mA load and 5V output will produce (24-5)V x (150+10)mA=19Vx160mA=3040mW or just over 3W (definitely needs heatsink). this is why one uses switching regulator or converter when in/out voltage difference is big. check mouser, newark, digikey etc: http://www.mouser.com/search/refine.aspx?Ntt=418-EC3AE21M%09 http://www.mouser.com/catalog/631/1734.pdf http://www.mouser.com/catalog/631/1744.pdf

[BobLfoot 302]

Have you checked out SOLA The SCP30D524B-DN model and the GLD-03-040 model might fit your bill.

[justwhy2003 0]

Thanks The 5 volts is only required for a pressure transducer that consumes only 2.5 mA maximum, the space requirements arent a big issue but the budget would be under £30 sterling if possible. It seems like a voltage regulator or a dc to dc converter such as the one you have reccommended would suit the application but it for some reason it seems TOO simple if you know what i mean. Im going to go with a 24 volt supply and the following device: rswww.com, catalogue number 168-513. its a dc to dc converter that supplied 5 volts at 400mA. Ill use this and monitor the operation for a period of time. Justwhy2003

[milldrone 0]

Justwhy2003, If price is a major concern how about a canabalized PC power supply? Chances are you have a PC laying arround not doing anything but just acting as a door stop. At this link are some suggestions for making one http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM . Vaughn

[panic mode 246]

for only 2.5mA you can use anything. cheapest solution is zener diode and resistor (zeners can be found for 4.7 and 5.1V) but I would go with regulator (you really get 5V, it's single component and it costs 15 cents, just extend wires and mount it directly on terminal strip). you can use either 7805 (TO220 housing) or 78L05 (smaller, no metal parts exposed, could be hanging free supported by the three wires attached to the terminals). TO220 housing comes with metal tab so you could bolt it to back panel and just use small 3-pin connector (like canibalized audio cable from older CD drives) and wires comming out to terminals.