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Coil voltage question

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jpc View Drop Down
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    Posted: 09 Mar 2018 at 09:06
Can someone explain to me:

The ignition coils are connected in series, not parallel on all Tonti big blocks.
So each coil only gets 6V, yet 12V coils are recommended.
Or do coils affect current differently from, say, lightbulbs ?

Thanks.
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 10:55
You must first of all state what ignition system you have, the most important factor.
 
I assume you actually have a Rita system which does indeed use two six volt coils in series. With that system you get sparks on both cylinders every revolution. Often called a wasted spark system.
 
If the supply is 12v, then you either must use two 12v coils, one for each set of points, or ignition amp, or in the case of this Rita, you use two 6v coils in series. 2x6=12 of course.
 
On the Rita you can also use one 12 volt twin output coil which simplifies the wiring a bit.
 
But in all cases, coil voltage (or voltages) must equal or add up to the supply voltage.
Exactly the same as a light bulb. You could run two 6 volt bulbs in series on a 12 volt supply.
Brian.

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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 11:16


As far as I know only wasted spark type electronic ignition system would use two 6V coils in series. (There is however another variation of Rita that uses 2 x 12V coils, but separated by diodes.)

In every case where contact breakers are used, must be 12V coils. Unless electrical system is 6V based of course. (6V battery.)



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iansoady View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 11:18
I'm sure I've seen somewhere in the last few days that someone is building replica RITA circuit boards. If and when I find it I'll post details.
Ian
1952 Norton ES2
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1958-ish Greeves/Triumph in progress
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 11:29
It's still a bit foggy to me, in part because the voltage rating is never stamped on coils.

I run a Dyna III ignition on my T3. Two triggers, so 2 sparks per 2 revs, no wasted spark.
When I bought it the seller was adamant I needed Dyna coils, but they're massive, I couln't find a satisfactory way to mount them, so I've been using the original (points) coils, tens of thousands of Kms, no problem.

The Dyna III has a "black box" which I suppose is an amp.

You say "in all cases coil voltages must add up to supply voltage", yet two 12V coils are recommended.
(2 x 12 = 24) Or is it the case that being connected in series, they operate at 6V ?  (2 x 6 = 12)
Then why should they be 12V coils ?  Confused Confused Confused

Thanks for your patience.
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 11:52
Yours is not wasted spark tho, which is what Brian was talking about.

I found this diagram, is this like yours?


https://tops-stars.com/wp-content/uploads/2017/09/dyna-2000-ignition-wiring-diagram-dyna-2000i-ignition-in-dyna-2000-ignition-wiring-diagram.jpg


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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 11:55
This is mine:

Image result for dyna III wiring diagram guzzi twin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 12:08
Originally posted by Mike H Mike H wrote:

Yours is not wasted spark tho, which is what Brian was talking about.

I found this diagram, is this like yours?


https://tops-stars.com/wp-content/uploads/2017/09/dyna-2000-ignition-wiring-diagram-dyna-2000i-ignition-in-dyna-2000-ignition-wiring-diagram.jpg
In that situation the two 12 volt coils are in parallel, you have two separate pickup sensors, one for each pot. Each coil is triggered from its own pickup.
 
In the case of the Rita, there is only one pickup and both coils are triggered simultaneously from that, both 6 volt coils being in series.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 12:28


[/QUOTE]
In that situation the two 12 volt coils are in parallel, you have two separate pickup sensors, one for each pot. Each coil is triggered from its own pickup.
 
In the case of the Rita, there is only one pickup and both coils are triggered simultaneously from that, both 6 volt coils being in series.
[/QUOTE]

And in my case, two pickups and two 12V coils in series (red + blue/black + white voltage input),
just as for points ignition.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 14:04
Points ignition will always run both coils in parallel.
 
In your case the supply 12v is white, which goes to both coils (parallel) and the red (from the right) and green (from the left) wires from the coils go to the amp which puts an earth on (or breaks it) when the pickups tell it to.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 15:04
Sorry to insist Brian, Guzzi points ignition diagram shows white (supply) going to coil 1, and from there to coil 2. That's series, and was the case on my bike when it ran points.

The Dyna III setup muddles things because an extra red then goes to the amp (to power it I assume, that makes 3 items in series).

The second red wire and the green wire are the "breakers" that fire the coil when the pickups intervene, yes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 15:37
If you're referring to the diagram you've posted above, they are in parallel. You'll get 12 volts via the white on the top coil, and via the blue / black on the bottom one. They will be earthed via the red and green wires respectively.
Ian
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1958-ish Greeves/Triumph in progress
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 16:15
OK !  I finally get it, coils are not quite like lightbulbs, they can be parallel connected with just one wire going from one to the next, because they're independently earthed !

I've already thanked you for your patience, but didn't elaborate on how thick I could be. Embarrassed

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 09 Mar 2018 at 19:59
You can do exactly the same with a light bulb, in fact that's the normal setting with many if you look at the wiring diagram. Just think of the tail light and front pilot (parking) light. Both are switched on by one switch so are in parallel.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 10 Mar 2018 at 10:59
Originally posted by iansoady iansoady wrote:

I'm sure I've seen somewhere in the last few days that someone is building replica RITA circuit boards. If and when I find it I'll post details.


Found it: http://www.rexs-speedshop.com/epages/es143131.sf/en_GB/?ObjectID=74341980

£74 seems a decent price.
Ian
1952 Norton ES2
1986 Honda XBR500
1958-ish Greeves/Triumph in progress
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