The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Greybeard on 27.10. 2012 12:42
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Hello electronics expert,
I'm thinking that I should be able to use a bi-colour LED to illuminate my ammeter. The LED would glow red when the battery is discharging and green when charging.
I'm thinking this might be a very simple circuit. What do you think?
Thanks
Neil Ives UK
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Neil,
There would probably be no circuit required at all because LED's only light when current flows through them in one direction. When a battery charges, current flows one way and when it discharges, current flows the other, so they could be connected in parallel just reversing one of them and then connect them across the ammeter shunt terminals, or if that doesn?t produce enough voltage wind a few coils of wire and connect it in series with the ammeter and put the LED?s across that. Some protection from overvoltage should maybe be considered, but a series resistor for each LED should suffice?
Phil
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Neil,
There would probably be no circuit required at all because LED's only light when current flows through them in one direction. When a battery charges, current flows one way and when it discharges, current flows the other, so they could be connected in parallel just reversing one of them and then connect them across the ammeter shunt terminals, or if that doesn?t produce enough voltage wind a few coils of wire and connect it in series with the ammeter and put the LED?s across that. Some protection from overvoltage should maybe be considered, but a series resistor for each LED should suffice?
Phil
You can't put resistances in series with the ammeter.
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Triton Thrasher,
I'm sorry, but I have to diasagree, of course you can, provided it is low resistance. After all, that is what the shunt of the ammeter is, i.e. a low value resistor with a meter across it to measure the voltage dropped!
Lets assume that the dynamo has the capability to produce 8 amps of output at full tilt (Probably a little optimistic for an A10, but bear with me!) Most commercially available LED?s operate at 3V(ish)
Using good old Ohms law V/I=R where
V= Volts
I = Current in Amps
R = resistance in Ohms
3/8 = 0.375 of an Ohm. Like I said, a few turns of wire, hardly a ?resistor? I?m sure you will agree? If you are particularly worried about dissipating this much energy , a simple solid state circuit could be constructed. Give me a little time and I'll come up with something...
Phil
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Before we get too technical; can I simply connect a two colo(u)r LED across the ammeter to achieve the desired aim?
Neil Ives UK
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Before we get too technical; can I simply connect a two colo(u)r LED across the ammeter to achieve the desired aim?
Neil Ives UK
No.
That's the simple answer mate! There won't be enough voltage dropped to give the 2 -3 Volts required to light them. You would need a circuit like the one below, that I just scribbled down, but before you go off and build it, I have to say that I have done absolutely no calculations and I would need to experiment with values and test it before I could state categorically that it would work OK. There would probably need to be some overvoltage protection for the solid state components too, in the shape of a Zener diode or similar. These kind of circuits seldom end up as simple as they first seem!
Phil
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Hi Moto, Neil and All,
Motorcycle Ammeters are NOT shunt Ammeters as described
They are whole current meters, there are only a couple of turns of heavy copper wire inside
when current flows one way the magnetic field created moves the little steel piece one way (attached to spindle and needle) then opposit current reverses the magnetic field and the needle assembly moves in the opposite direction,
I have a circuit somewhere that uses opamp chips to light individual LEDS the indicates voltage
depending on the range its built to it can have red leds for 9,10,11v and green for 12,13,14
HTH
John
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Hi Moto, Neil and All,
Motorcycle Ammeters are NOT shunt Ammeters as described
They are whole current meters, there are only a couple of turns of heavy copper wire inside
when current flows one way the magnetic field created moves the little steel piece one way (attached to spindle and needle) then opposit current reverses the magnetic field and the needle assembly moves in the opposite direction,
HTH
So a couple of turns of heavy copper wire are?.... a resistor and an inductor, we are all really describing the same thing and what I have said still stands regardless of the construction of the ammeter itself.
Phil
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Very interesting idea!........... This item may be of interest to you? I may fit one myself. Note that they do one to fit in a 8 millemeter hole that has an in-line circuit board. E-Bay item number 150479033981. Cheers!
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Moto
"I'm sorry, but I have to diasagree, of course you can, provided it is low resistance. After all, that is what the shunt of the ammeter is, i.e. a low value resistor with a meter across it to measure the voltage dropped!"
The motor cycle ammeter does NOt work on voltage drop!! simply the magnetic effect of a a copper coil
A shunt ammeter does, it measures the voltage drop across a low resistance (Shunt) using a millivolt meter
A different principle entirely *ex*
John
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A shunt ammeter does, it measures the voltage drop across a low resistance (Shunt) using a millivolt meter
John
Agreed, but as mentioned before, the mechanics of the ammeter are completely immaterial (unless you are trying to score points off me) so could you please tell me how it affects everything else I wrote ????
Phil
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Neil... what you want is something like this... http://youtu.be/_5Xp__fiY6g ... The multi coloured monitor LED is just above the ammeter you can see it change colour as engine is revved and then a load applied. The blue LED on the left is a high beam indicator and the red on the right indicates the brake light.
Thanks Metalflake for the link to cheaper battery status monitors!
I have them fitted on all my bikes and find them quite useful. Today I took the A10 out and for the first short distance there was no charge but green light soon lit up a further few miles down the road, I guess the dynamo may have lost its magnetism due to standing unused for a while.
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Moto,
Going back up to your suggested 0.375 ohm resister, this would drop 2.25 volts across it
at 6 amps (60 watt dynamo 12 v system etc )
Have you a source of 10 v headlight bulbs ? *smile* *smile* *smile*
Good night
John
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No worries LJ! With regards to the brake light indicator, is it wired in to the switch or a fibre optic wire from the back light? I have done the fibre optic thing on my '78 Bonnie and it works a treat. At night I know for certain I have a back light and stop light, and in the day it is still bright enough to tell me if the brake light is on too.
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John,
The last time I examined an A10 wiring diagram the lights were powered from the battery? not the charging circuit! The standad A10 is 6 volts.
Is this a 5 minuite argument or the full half hour *smile*
Good night
Phil
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MetalFlake... That's a good idea about using fibre optic cable, I wired my brake indicator light to the switch. I've found that the brake switch is prone to being knocked which then does not allow it to work properly. The panel indicator is very reassuring, how many times have we had to check only to find the brake lever needs lots of pressure to light the bulb up, or the darn thing is already on!
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The standad A10 is 6 volts.
Indeed it is, however there is one exception. The speedo and rev counter bulbs are, according the the owners instruction manual 8v 3 amp.
John
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Crikey! 8 V, 3 A speedo and rev counter bulbs. That's 48 W between them!
But going back to the original question, maybe I've missed the point, but if the ammeter is illuminated, can't one then see how much charge/discharge there is?
Ken.
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Crikey! 8 V, 3 A speedo and rev counter bulbs. That's 48 W between them!
I apologise for the typo, that should have been .3 amp!!!!
John
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I apologise for the typo, that should have been .3 amp!!!!
Ah, I thought perhaps you'd been looking at a Haynes manual *conf*
Ken *smiley4*
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Crikey! 8 V, 3 A speedo and rev counter bulbs. That's 48 W between them!
But going back to the original question, maybe I've missed the point, but if the ammeter is illuminated, can't one then see how much charge/discharge there is?
Ken.
I've seen ammeters illuminated by "leaked" light inside the headlamp shell.
I think the point you're missing is Man's desire to put extra bits on his bike.
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Back to Neil's original query, here is an idea for such a colour change indicator based on ammeter current (via voltage drop in the small coil resistance). *idea*
A pattern ammeter showed about 6 mohm resistance. Note this circuit is unproven but based on something I did way back when. The 200k value can be varied to suit 6 or 12 V, and transistor gain.
This could be described as a common base comparator, not too far removed from Electronics 101, but perhaps not that obvious. Big plus is that no extra supply required as for the earlier circuit.
Yes Ken, it's that just because you can thing, but a changing colour glow from the ammeter (assuming used to illuminate the instrument) would add deliciously to the paranoia if your charging system is at all dodgy. Fit electronic ignition for best effect *smile*.
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Oh Mike
Moto wont be happy with negative earthe either not to mind 12 v conversions *eek*
*smile* *smile* *smile* *smile*
John
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For anybody interested. I got the fibre optic cable off e-bay, in the model railway parts. Apparently they use them for the headlights on the engines. The bloke I got them from was in Stockport. I finished the job off by getting a small block of aluminium and drilling half way through the thickness of the outer sheath and the rest the thickness of the fibre. Trim the end and polish it (it makes it shine brighter that way) flush. I then glued it to the side of the headstock right where I can see it, and now I know what is going on inside my rear lens at a glance, day or night.
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Back to Neil's original query, here is an idea for such a colour change inductor based on ammeter current (via voltage drop in the small coil resistance). *idea
SNIP
Yes Ken, it's that just because you can thing, but a changing colour glow from the ammeter (assuming used to illuminate the instrument)
Many thanks Mike. That looks doable. I really need a 6v positive earth version though.
Yes, my idea followed on from thinking about how best to illuminate the ammeter.
Neil Ives UK
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Neil, one of my previous posts gives an e-bay listing number that will give you what you want. I put it there for you specifically and they do a six volt version if you read it.
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Neil, one of my previous posts gives an e-bay listing number that will give you what you want. I put it there for you specifically and they do a six volt version if you read it.
I had a quick look at that device when you mentioned it and came away thinking it was only for a 12v system and that it was a bit too big for my needs. I see now that there is a small version and that they can do a 6v one. I'll contact them. Thanks for the tip.
Neil
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Crikey! 8 V, 3 A speedo and rev counter bulbs. That's 48 W between them!
But going back to the original question, maybe I've missed the point, but if the ammeter is illuminated, can't one then see how much charge/discharge there is?
Ken.
The ammeter in the cowpat style cowl is on the side and not that visible when you are riding. It doesn't have a dedicated bulb. I was pondering how to illuminate it when I thought of using LED's to show the charging state.
Neil
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Crikey! 8 V, 3 A speedo and rev counter bulbs. That's 48 W between them!
But going back to the original question, maybe I've missed the point, but if the ammeter is illuminated, can't one then see how much charge/discharge there is?
Ken.
The ammeter in the cowpat style cowl is on the side and not that visible when you are riding. It doesn't have a dedicated bulb. I was pondering how to illuminate it when I thought of using LED's to show the charging state.
Neil
Illuminate it with an LED!
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I guess I should know by now not to commence a design without an adequate specification *doh*
The LED current monitor circuit I posted can be converted for positive earth by changing to suitable NPN transistors (and reversing the diodes naturally enough). As I said the 200k bias resistor can be changed, starting at about 100 k for 6 V operation. This circuit is not available in a convenient guaranteed ready made product.
I set out to come up with a current monitoring device as Neil requested. There are indeed a number of LED voltmeter products on the market, including the Ebay one referred to by Metalflake. A Voltmeter measures voltage (electric pressure), and an Ammeter measures the current that flows (E101 again). These are not at all the same of course. There are pros and cons in monitoring either I or V on a bike, but the ammeter shows the detail at a given moment. An LED version of either would indeed illuminate the ammeter *ex*
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It's a pleasure Neil, I hope they work........ I am about to order one now!
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Another scheme that would work is a charge warning light, as used by cars with dynamos. It's just a small bulb wired between dynamo D and battery live. It would need a battery isolating switch for when you're parked, but that might be a good idea anyway.
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Yep, that's what I use on the cafe TT. Flick the switch it glows red, start and idle a dim glow and goes out with a few revs.
Cheers
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Yep, that's what I use on the cafe TT. Flick the switch it glows red, start and idle a dim glow and goes out with a few revs.
Cheers
I had a lazy dynamo that used to forget its polarity. Fitting a charge warning lamp actually cured it.
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Any idea how that woks Triton or Musk? I understand why it lights up, but why does it flicker and then go out?
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Easy, Metalflake.
When the generator is not turning, the current has a path from the battery through the lamp then through the armature to earth.
When the generator starts working, the voltage rises and when it equalises with the voltage from the lamp the lamp will be extinguished as the voltage on either side of the lamp will be the same, therefore no possibility of current flowing to earth.
Trev.
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Trev that's the most useful 'useless piece of info' I've read in a while!
I'd've used that bulb as a test light and then spent years trying to figure out why it works sometimes, but not otherwise....
Beaudy, it's on my list of things to keep in mind, cheers
S'pose I use LED (in 6v combo) and hooked up the right way, wouldn't glow unless something amiss negating the need for isolator (still working on that theory, made it up as I went along-as I do)?
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Thanks for that Trevinoz. Well explained!
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Dutch,
I'm not sure what you want to do.
If you connect an LED it will glow the same as an incandescent lamp and go out when the voltage equalises.
Much less current draw so could glow for a long time before discharging the battery when the bike is not running.
Trev.
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Thanks to everyone who got involved with my request.
Neil Ives UK
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Neil, fitted the one off e-bay today. Just about as easy as it gets really to wire up and the best bit is, it works a treat. However what may interest you more, is the fact that you can get it without the bezel fitted which means you can fit it into your ammeter with ease. It would require a hole of about 3/16" pop it in, seal with a splash of silicone and it will illuminate your ameter as a bonus. To do this though you will have to order the smallest one and ask him not to fit the bezel before he sends it.
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Neil, fitted the one off e-bay today. Just about as easy as it gets really to wire up and the best bit is, it works a treat. However what may interest you more, is the fact that you can get it without the bezel fitted which means you can fit it into your ammeter with ease. It would require a hole of about 3/16" pop it in, seal with a splash of silicone and it will illuminate your ameter as a bonus. To do this though you will have to order the smallest one and ask him not to fit the bezel before he sends it.
Thanks for the feedback.
Neil
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Neil, fitted the one off e-bay today. Just about as easy as it gets really to wire up and the best bit is, it works a treat. However what may interest you more, is the fact that you can get it without the bezel fitted which means you can fit it into your ammeter with ease. It would require a hole of about 3/16" pop it in, seal with a splash of silicone and it will illuminate your ameter as a bonus. To do this though you will have to order the smallest one and ask him not to fit the bezel before he sends it.
I have just ordered one of these gizmos. I'm thinking that I will need to be able to disconnect it when not required but of course I don't have an ignition switch so I may make a 6v relay operated by the lighting circuit: I only need it in the dark.
Neil Ives UK
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Hello Neil, Two ways to do it, an on/off swiich on the earth side of the unit, letting you run it night and day. Or connect the live to the back light which would have the unit only working when the lights are on. If your pilot light works on dip and main beam that would work too. It does only have a tiny drain on the battery though, and I have left mine on all the time (12v 3ah battery). The reason behind this is that the smaller unit looks very much like an alarm warning light, which is a bonus! Personally I would go for the first option in your case simply because it is better to find out the bike is not charging in daylight, than at night. At least that way it gives you the chance to get parked up before darkness sets in.
Cheers Rob
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Hey Trev, I forget all of what I had in mind back there, a combination of ideas, but will have a play, and if it works will get back to you
I find LED potential quite fascinating, thanks guys
cheers