hello , for my project I need to power 12 4.8v-6v servos. I spoke to a man in maplins(a british electronics shop) who recommended a regulated dc power supply with the following specs
input voltage 230v
output voltage dc 13.8v
output current 2a continuous
3a 50% duty cycle
5a surge
I purchased this unit , then decided to test it , using ehternet cable soldered to cut jumper wires I connected the positive point to the positive rail on my bread board and the negative point to the negative rail. I then pinned the negatives of 2 of my servos to the the negative rail and 2 of the positives to the positive rail. obviously my signal wires went to the digital pin specified on my sketch.
I turned it on and at first it worked , however after about 1 minutes my servos became sluggish and then stopped completely. fearing I might have broken them I tried each one on its own, using the 5v and gnd port on my arduino, they were both fine. I then thought that my supply had stopped producing current. I don't have a voltmeter so stupidly I decided to test it on an LED which burnt out immediately (I kept a bit of cloth round the LED in case it exploded).
does anyone know why my servos have stopped turing when drawing power from my supply , have I wired it incorrectly ? , is 2 too smaller number to test on?
any help would be greatly appreciated , thanks
sam
from the looks of things should I have used a 6v regulated supply? the man in maplins implied that because the current would be split between 12 servos the fact that the regulated power supply gives 13.8 volts would be okay?
samhallett:
from the looks of things should I have used a 6v regulated supply? the man in maplins implied that because the current would be split between 12 servos the fact that the regulated power supply gives 13.8 volts would be okay?
Yes you were mislead by a salesman that didn't know squat about electronic apparently. A servo requires 4.8 to 6 volts, I'm very surprised you didn't destroy your servos by applying 13.8 vdc to them. If you do end up with multiple power supplies be sure you connect all their ground (negative) terminals together and to a arduino ground shield pin. You will most likely fine more selection and better prices if you look for regulated 5vdc supplies rather then 6vdc supplies.
ok thank you , I'm very non-savy when it comes to current , is there a way calculating the amount of 5v regulated supplies I would need using the ampage?
also I goggled ground shield pin , is this a shield that needs to be purchased separately or a pin on the arduino
also most of the 5v power supplies I've seen end in a jack but I'm assuming I could strip that and I would find a positive and ground wire inside?
cheers
sam
It would have been fine if it was a VARIABLE supply and you had set the voltage to +5Vdc. Too late now.
Assume each servo needs 1 amp of current at 5v or 6v. That means 12 amps for 12 servos. If they won't all be moving at the same time a lower current may be sufficient - but not less than 6 amps, I suggest.
The Arduino ground pin just means any of the GND connections on the Arduino board.
You can either cut the jack plug off the power supply output to get at the wires or (perhaps more sensible) buy a socket to match the plug and connect your servo wires to that. Make sure you know which wires is positive and which is negative/ GND.
If you don't already have one a cheap digital multimeter is almost essential for Arduino stuff.
...R
5V, 15A or 5V, 20A would give you some margin.
Cheapest solution would be to re-purpose an old PC power supply, they can often be gotten for free and have more then enough 5vdc amps capacity. Lots of info on the web on how to modify them for standalone use outside of a PC.
thanks , I'm a little pushed for time as my projects got to be in in 2 weeks and theres allot to do so I think i'll just try and find one to buy for now , good tip for the future though.
would this be ok for the purpose
http://www.ebay.co.uk/itm/DC-5V-15A-Universal-Switching-Power-Supply-for-LED-Strip-CCTV-or-other-use-UK-/251435767679?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item3a8abd577f
the numbers look right and fom what I read on wikipedia it seems like the fact that its a switching power supply shouldn't make much difference, just wanted to check so I do't buy another un-fit for purpose power supply.
cheers
sam