A challange ....

[Allan]

Okay you guys, there are numerous posts on this forum about electrics being fried, so heres a challange for you.

Can someone make for sale, or find for sale, a unit that will suplly a constant 12 volts to our valuable equipment (Comms, GPS, Phones, MP3 players etc) even when the rectifier starts to go tits up.

It would be far better to have a small replace-able item go pop than all that other expensive kit.

It only needs to be something small to fit under the seat, that all our extras can be tapped into.

So over to you - maybe if you find something appropriate Jaws and Pete could start stocking it!


Buzz.

 

[gypsy]

i think they call it a fuse?

 

[derek kelly]

i think they call it a fuse?

Nah! That's a chocolate bar and it would melt.

 

[Allan]

i think they call it a fuse?

Nope - wrong.:t

A fuse is inline protection against a unit drawing too much current, it melts if it too many amps pass through it.

It dosent stop higher voltages passing through it, hence you can use all types of fuse wires on given voltage and the circuit will work.

Example - Put 5 amp fuse wire in a cooker circuit, swith the hob light on and it will work, switch one of the rings on and the fuse will pop.

Buzz

 

[gypsy]

so your looking for a miniture "surge protector"?

 

[Adam Rickenberg]

Electrickery problems....

If your rectifier goes "tits up", then there is nothing that a regulator can do about it. The regulator is fed from the rectifier and is dependant on the rectifier.

To explain: the AC current is rectified to DC current (as per Lumpy's statement) and is then fed through a regulator to the main BUS circuit. The bird has a built in regulator alongside the rectifier circuit, all fitted inside the aluminium housing........ The voltage supplied to the battery & main BUS circuit should be 15.5 volts (Measured at the battery terminals) with the bike running at 5000rpm and the main headlight on high beam.

If you are not getting a constant voltage to the battery of at least 14.5 volts, then you may have some loose connections between the alternator and the battery, or rectifier/regulator may be on its way out. However, the more electronics you put on the bike i.e. heated seat, heated grips etc... the lower the charging voltage will be because the current draw on the charging system will be higher.

The alternator on the bird only produces 460 watts....... so add up how many watts you are demanding from the system and see where you stand.

 

[Jaws]

Ok.. what you want is a Thyristor, a 12v zener diode, a 10 Ohm ( or there abouts.. dont really matter ) 1/16w resistor and a fuse in a holder..

Configure put together a nice little crowbar circuit and all is protected

 

[Jaws]

Ok,, to pre-empt the requests, here is a full circuit diagram..

Please be aware the fuse is EXTREMELY important.. Leave it out and you risk fire and all sorts !!

There is very little kit that will not easily take 16 volts ( inc Autocom which, looking at the circuit should be able to handle much more than that even ! It really is bloody well designed stuff )
The feed comes in from the left and the protected lines leave on the right

 

[R2B2]

Will a light bulb take 16 volts....?

 

[Jaws]

Orrrr...
Rather than put a crowbar circuit in, what about simply controlling the celivered voltage with a simple device like this..

( Of course, ideally use this to control and put the crowbar after it for complete protection )
( orrrr, replace the R and zenner with a 7812 device but that has a max input of 19v or so ( I think ) which may blow if the reg rec goes zap..

Ahh.. just noticed.. That capacitor across the output.. its just a .1 uF or similar.. not exactly critical, just there to stop in going into free running oscillation..

 

[Jaws]

Yes Rob, a bulb will indeed take 16 volts easily ( and actually for quite a while too, normally )

 

[gypsy]

i knew you needed a fuse

 

[Allan]

Orrrr...
Rather than put a crowbar circuit in, what about simply controlling the celivered voltage with a simple device like this..

( Of course, ideally use this to control and put the crowbar after it for complete protection )
( orrrr, replace the R and zenner with a 7812 device but that has a max input of 19v or so ( I think ) which may blow if the reg rec goes zap..

Ahh.. just noticed.. That capacitor across the output.. its just a .1 uF or similar.. not exactly critical, just there to stop in going into free running oscillation..

Okay okay - you've lost me... :h

All I want is something to stop a voltage surge frying my equipment - so have we got one?

I know the rectifier puts out more than 12 volts, but I only want 12 volts (no more) going to my GPs etc

So again, have we got one?.:dunno:

Buzz

 

[gypsy]

i could possibly steal one ?
but you wouldn't buy anything that was stolen :dunno:

 

[Adam Rickenberg]

Jaws

Can you modify your circuit to take a 7812 regulating transistor??

That will give exactly 12 volts..... but I dunno how many watts the 7812 can handle :dunno:

You should be able to get an RS catalog and look up the appropriate item.....

 

[Jaws]

Forget the 12v Allan.. everything you can buy today is happy up to at LEAST 16v..

However, if you want to max the supply at 12V then simply change the value of the zenner diode to 12.6v and you will get a controlled 12v across the output

 

[ianrobbo1]

:dunno:

 

[Murt]

Ian, I concur.
Murt

 

[Jaws]

Can you modify your circuit to take a 7812 regulating transistor??

That will give exactly 12 volts..... but I dunno how many watts the 7812 can handle :dunno:

You should be able to get an RS catalog and look up the appropriate item.....

The problem with that is twofold Adam.

The first issue is that if the input voltage goes above about 19v the device ( it is an IC rather than a transistor ) could blow to short..

The output voltage would indeed be 11.4 v because there is a .6v drop across any transistor junction..
Hence the use of a 12.6v zenner to put the base of the output device .6 v higher than the desired v at the emiter

Adendum..

I just checked and the later 78 and 79 series devices can now take up to 24v input which is handy ... But apparently you really have to be a tad careful when using them in autromotive stuff cos any AC ripple can set them oscillating .. and if thhey go into runaway they may as well not be there at all !

So a nice little bridge and about a 25000 uF cap needs to go in before the device to smooth out any stuff eminating from the alternator

 

[Trumpet]

Why do you want to make a 12v crowbar circuit when you know you can see 15-16v when you rev it ?? :dunno: Maybe a 17 or 18v crowbar and an LED to warn you have gone overvoltage and it has shut down the DC (popped the fuse)