Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: offshore1987 on June 02, 2008, 06:01:30 PM

Title: Getting 4.8v to 1 or 1.2 volts?
Post by: offshore1987 on June 02, 2008, 06:01:30 PM
Hi peeps

I got a radar unit at the show yesturday and trying to set up my tito s/s, i had planed to use a reciver pack 4.8 v to power everything ( lights, radar ) and i want to use me hunter power board i also got yesturday, but when i put the 4.8v through the radar unit, it gos into spazo mode  {-) and i dont think many radar units turn at 300mph  ;)

How can i get the voltage down from 4.8v to 1 or 1.2v? Its kinda confused me as im not so good with electrics

All the best
Title: Re: Getting 4.8v to 1 or 1.2 volts?
Post by: alan colson on June 02, 2008, 06:21:24 PM
Try using a single 1.2 volt nicad cell, they do make holders for single cells so that you can change them. You may also find that an ordinary 1.5 volt AA battery that is to low on power to run your radio may well run you radar.
Title: Re: Getting 4.8v to 1 or 1.2 volts?
Post by: John W E on June 03, 2008, 01:02:54 PM
Hi there

A while ago, whilst doing a web search, I came across a very simple electronics circuit for controlling the speed of a small electric motor.   This circuit would be ideal for those who wish to drive radar.  I originally built the circuit and it is now in the Cervia Tug, driving the Cervia's radar.

The circuit is based on the principle of our electronic speed controllers, in other words, it pulses the motor.

So, at extremely low revolutions, we do tend to get a 'jerky' effect.   To overcome this, I put a belt drive on, with a 1/4'' pulley on the motor and about 1 1/4'' pulley on the radar shaft.   This gives me a fair representation of the speed of a radar going around.

Originally, I was going to do a build, a may still do the build for the Forum of this little circuit.

One of the most difficult things though to get across is to make people understand that electronics arent a great 'black art' to be frightened of.   We dont need to be mathematicians to understand forumulaes that sometimes go with the electronic circuits.  We dont really need to understand Ohm's law but, sadly, what we must do is educate or explain the components so...when people go to shops such as Maplins and ask for a capacitor or a variable resistor they have a fairly rough idea of what they are looking at.   Sadly to say that the big downfall of this are the big electronics shops such as Maplins, because, one of the things I did when I first built this circuit was try and order the components over the telephone from Maplins.   You guessed it - I got a 'dippy' person on the other end of the phone 'havent got one of them, what is that' was the answer.  :o

I suppose then, that says it all - doesnt it.

I eventually ordered all my components - 3 lots so I could make 3 units up from ESC who are based in North Shields and the sum total - with postage and packing was a little over 7 pounds sterling.  I have included, for those who wish, a copy of the circuit diagram and also of a picture of the actual unit which I have built for those who wish to make one.

Possibly one day in the future, I will get around to putting the build on the Forum.

For those who wish of course.....

john e
Title: Re: Getting 4.8v to 1 or 1.2 volts?
Post by: roycv on June 03, 2008, 02:14:27 PM
Hi all, my first thought was to put several 1 amp diodes in series with the motor.

If my memory serves me you drop about 0.7 volts across the junction, so 3 diodes will drop about 2 volts.  I think it will work and it is cheap.

regards Roy
Title: Re: Getting 4.8v to 1 or 1.2 volts?
Post by: offshore1987 on June 03, 2008, 02:27:11 PM
Thanks for taking the time to reply guys  O0 il be giving them ago

Cheers :)
Title: Re: Getting 4.8v to 1 or 1.2 volts?
Post by: John W E on June 03, 2008, 05:36:00 PM
ooops senior moment - for those who are a little bit frightened of doing electrical stuff, have a word with FLJ, but here are the parts for those who wish to have a go at it themselves.   Perhaps FLJ will have a go at building one first and trying it out - maybe altering one or two components to try and get it to work even better  O0 O0

PART     TOTAL       DESCRIPTION           

R1             1           1 Meg  1/4W Resistor
R2             1           100K Pot
C1             1           0.1uF 25V Ceramic Disc Capacitor
C2             1           0.01uF 25V Ceramic Disc Capacitor
Q1             1          IRF511    MOSFET           SUBSTITUTE                                               IRF620
U1   1          4011 CMOS NAND Gate
S1             1          DPDT Switch
M1             1           3-6 volt motor
Title: Re: Getting 4.8v to 1 or 1.2 volts?
Post by: malcolmfrary on June 04, 2008, 10:55:06 AM
If you tire of the McFries rejects at Maplin, try here
Handy for Bluebird, opposite Cullercoats nick.