what size power adaptorshould i use for model power and walthers street lamps

[jmk3438]

HEY GUYS..  i am planning of hooking of about 11 street lights from model power and walthers using a DC  power adaptor (12 volts) ..what do you recommened for amps or milliamps?    i am thinking around 500 MA........

 

thanks

[el-capitan]

This will depend on what bulbs you are using. 500 mA should work. I always save old power packs from electronics that are being thrown out and use these for powering my lights.

What may be more important is the voltage of the bulbs and if they are wired in series or parallel (or both). I am using a 5 volt power supply and 1.5 volt bulbs. So, in order to not overpower the bulbs I need to run 4 in each series (5 volts/ 4 bulbs = 1.25 volts per bulb). So far I have installed and powered 4 series (16 bulbs total) off a 1 amp power supply. 

Running more than 4 in each series causes them to be too dim.

Not sure how many more I will be able to run off the same power pack but I will know when I get there.

 

[rrinker]

 What you need to know is the current rating on the bulbs. If it's 30ma, then 11 of them in parallel will work fine with a 500ma power supply, as the bulbs will draw 330ma. Never laod the pwoer supply to the maximum, 75% is a good rule of thumb.

 Simple principles to remember: devices in series ADD voltage but SHARE current, devices in parallal ADD current but SHARE voltage.

 So if you have 1.5 volt 30ma bulbs and wire 4 in series per above, so each bulb gets 1.25 volts on a 5V power supply, the 4 total will draw 30ma. You can then place another set of 4 identical bulbs in series, and wire that string in parallel. You now have 8 bulbs total, drawing 60ma from the power supply. The downside of anything wired in series is that if one fails, the whole string goes out. The benefit is it is an easy wya to get the lower voltage needed for some bulbs. Runnign 1.5V bulbs on 1.25V makes them plenty bright but they will last a lot longer than if run at the full 1.5V. If the bulbs you are using are rated rfor 14-16V, try them on a 12V power supply They should still be plenty bright but they will also last a long time, unless you snag one and break it while reaching over.

                             --Randy