servo power supply

[rob nash]

hi,
I need some advice on a regulater for servo, am after powering a servo project from a mains adapter Ive tried a lm7805 ok with one may get away with 2, I've seen LM338T variable 5A is this a siutable regulater to power 7 servos i'd be greatful if someone could offer any advice.
thanks rob

 

[MFB]

You first need to be sure the mains adapter is able to provide sufficient current, without the voltage dropping to less than about 2.5V above your regulator output (e.g. 7.5V for an non-low drop regulator like the LM7805). This will be difficult for multiple servos because the total draw will depend on whether each is up and running or starting, and also their mechanical loading. It would be a good idea to conduct some tests using a big bench power supply with a current readout.

 

[rob nash]

hi
thanks mfb

You first need to be sure the mains adapter is able to provide sufficient current, without the voltage dropping to less than about 2.5V above your regulator output

I did'nt even think if the adapter in my hand could supply the 5A lol "what it is" is a 300mA3.6VA "failed before i began".

It would be a good idea to conduct some tests using a big bench power supply with a current readout

going to crack open the piggy bank.
thanks for the reply

 

[srnet]

hi,
I need some advice on a regulater for servo, am after powering a servo project from a mains adapter Ive tried a lm7805 ok with one may get away with 2, I've seen LM338T variable 5A is this a siutable regulater to power 7 servos i'd be greatful if someone could offer any advice.
thanks rob

Impossible to offer advice at this stage as it depends on the Servos and what load they are under, they vary a great deal.

So the servos are ?

 

[rob nash]

hi,
srnet the servo's are tech's 4 dgservo s03nf std and 2 gbx013 http://www.techsupplies.co.uk/epages/Store.sf/en_GB/?ObjectPath=/Shops/Store.TechSupplies/Products/GBX013mini servo " made in china where else" AS for the load well its lump of polystriene wright now.Am after making an animated head for a bot project.
I do have sharman regulated dc 13.8V 3A just got to brush of the dust and a mm

cheers rob

 

[erco]

Servos can pull well over an amp each, depending on loading. If they all move at once, you could be looking at 10+ amps. That's gonna be hard on your PS and regulator. If your servos are intermittent use and it's a mains-powered project, you might consider using a small built-in batter (lead acid or NiMH) and constantly trickle charge it.

 

[rob nash]

hi all,
thanks for the reply's, erco your givin me food for thought i will google search a suitable circiut but for the mean time stick with my trusty battery may get another set, I,ve just found this site seems intersting http://www.circuitstoday.com/lead-acid-battery-charger
cheers rob

 

[rob nash]

hi,
I've come across these AC to DC 5 volts 12 Amp psu from rapidhttp://www.rapidonline.com/Electrical-Power/60-W-Chassis-Psu-5v-85-2276 and was woundering if these would be safe powering my servo,what am not sure about is the Amps would having 12 Amps on the powerline burn the servo's when not underload.
cheers rob

 

[MPep]

More current is not a problem when things are good.
What you need to be concerned about is what happens if something fails,??? 12A is a large amount of current that can flow into a short circuit!

A load (the servos) will only draw enough current required, at the supply voltage.