Model Boat Mayhem

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: bill morris on July 01, 2015, 12:26:40 AM

Title: voltage reducer
Post by: bill morris on July 01, 2015, 12:26:40 AM
I have a voltage problem and I hope someone can help.i am building the Vic Smeed Lorraine and putting lights, sound etc.
My cabin lights, Nav lights are all 3 volts.
The radar is 1 1/2 volt  using Lipo batteries 11.1volt with a 30 amp esc.
I've seen some relays that go to 3volt but not 1.5.any help would be great.

Thanks and God bless everyone.

Bro Bill Morris
Title: Re: voltage reducer
Post by: inertia on July 01, 2015, 09:08:32 AM
I'm not at all sure I understand what the problem is here.
Relays won't reduce voltage on their own - they are just electro-mechanical switches. The voltage ratings you see for them generally refer to the coil, not the contacts (which can switch 1.5v easily).
You'll be hard-pressed to find a simple voltage regulator to drop 11.1v down to less than 5v - the power dissipation would be considerable. Some variable ones might do the job with other components but you'd need two such circuits - one each for 1.5v and 3v. Sounds complicated and expensive.
I would suggest that you run the lights from a pair of NiMH cells (2.4v) and use a single battery to run the radar. Radar sweep arms tend to run all the time so don't bother with a radio switch for those.
Hope this helps, even if it's perhaps not the answer you were looking for!
Dave M
Title: Re: voltage reducer
Post by: Martin [Admin] on July 01, 2015, 09:25:46 AM
If you want to switch your lights, sounds etc. remotely, you can have at the various option here:

Title: Re: voltage reducer
Post by: malcolmfrary on July 01, 2015, 10:06:07 AM
When a voltage is quoted for a relay by a seller, it is usually the nominal operating voltage.  The manufacturer in his spec. sheet will quote a series of voltages, the lowest will be the lowest voltage that will allow the relay to operate, the highest will be that at which the insulation on the coil starts to melt.  The normal operating voltage will be somewhere in between. 
When voltage is applied, current flows and the coil becomes a magnet which moves a lump of iron called the armature.  This in turn operates a switch, or, in some cases, a bunch of switches.  This switch works a circuit that can be totally independent of the one working the coil, so a completely different power supply can be used very simply.  The restrictions are that the contacts have to be able to handle the current that the load will impose, and must also be able to switch, and switch off, the supply voltage without welding themselves.
Voltage reducing circuits that go down to RX voltage (look up BEC threads) are amazingly small and cheap because there is a huge market.  Other voltages are not, they are for a very small market and availability goes down and price up to match. 
Generally, an AAA cell will keep a radar motor going for days on end, and is lighter and cheaper than any voltage dropper.  Just a manual switch, or have the battery easily accessible for removal after use and insertion before.
If you use LEDs for nav lights, current requirements are very low, and a PP3 battery does very well.  If using 3volt incandescent bulbs, then, as Dave suggested, a pair of NiMH cells wired to give 2.4 volts will do the job.  The lights will under-run which will prolong their life and will make them look more like navigation lights.
Title: Re: voltage reducer
Post by: plastic on July 01, 2015, 02:15:13 PM
Why not just get a bit of Veroboard and some variable-output voltage regulators and then build yourself a set of power outputs at any voltage you want direct from the main battery?

An LM317 regulator ic will give you whatever you want from 1.25V upwards at up to 1.5A. Max input is 37V so battery applications are within that.

Just make a separate supply for each output required - they are availably in TO220 style so are easy to build a little circuit and are available from Ebay for a couple of pence each.

You can then junk all those other batteries that you are talking about - you just need the main drive battery.
Title: Re: voltage reducer
Post by: Time Bandit on July 01, 2015, 05:10:48 PM
I“d use those, perfect for radar motors, lights...

Just search for LM2596 on fleabay to find the cheapest version.
You can buy them in china for <1$ per piece.

By the way, are you going to use LED as light“s?
Then forget the 3V and adjust the regulator to around 4-5V and use proper resistors!!!
Title: Re: voltage reducer
Post by: The Old Fart on October 16, 2015, 06:42:52 AM
these are useful for reducing voltages, under £2 , can't make them for less.