reducing voltage not amps?

[harps]

(i meant to post this in general chat sorry)

hello, a new and inexperienced electrician here : )

i have a 17 volt ac>dc power supply and it can offer 1.1 amp

i hope to power a little relay which needs only approx 5v and 40 milli amps to trigger it. So when I use a variable resistor on the psu to drop the volts down to 5v, the amps drop too and so much so I cant power my relay with it. : /

i know the relay works at 5 v as i have another psu to test it with

maybe i need change the regulator inside this 17v psu?

thanks for any help. : )

 

[Hero999]

There's no need for a regulator, a simple series resistor will do.

Use Ohm's law

R = (17-5)/0.04 = 300R

So use a 270R resistor (the nearest E12 value) in series with the relay.

 

[harps]

thanks, i did try a resistor as you mentioned, it did reduce the volts but the current came down far too much for my relay,i connected it in series as you say : / might be something else i did wrong. anyway i bought a 5v regulator and it did the trick. it reduced the volts but the amps where still reading high on my test meter.

i made this type of circuit below and used a diffrent psu running at 10v (bringing it down to 5v using this circuit) the parts were so cheap i built the whole thing, as the relay was for routing audio the dc smoothing might have helped any noise crosstalk , well, its all for fun : P

**broken link removed**

peace : )

 

[Hero999]

thanks, i did try a resistor as you mentioned, it did reduce the volts but the current came down far too much for my relay,i connected it in series as you say

Then you've got the current consumption of the relay coil.

Measure the relay coil's resistance with a DVM and tell me what it is.