SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
View Poll Results: Whatís the most important thing to you?
Lowest possible cost 3 23.08%
Make it as small and light as possible 6 46.15%
Battery longevity is very important 3 23.08%
Highest power possible 3 23.08%
Highest RPM possible 2 15.38%
Only use through hole construction 2 15.38%
No winding of transformers 4 30.77%
Group buy of components including boards 0 0%
Group buy of boards only 1 7.69%
Iíd rather buy a kit with everything in it 0 0%
I want to buy a pre-built & pre-programmed system 0 0%
I only want to use a 4.8v Ni-MH battery 2 15.38%
I only want to use a 2S battery 1 7.69%
I only want to use a 3S battery 1 7.69%
I want to use a 4.8v battery to 3S battery 5 38.46%
I want to use only off the shelf parts from Digi-Key or Mouser 3 23.08%
I want the Timer board to be separate from the HV board 6 46.15%
I want a combination Timer & HV board 1 7.69%
I want all the options possible using jumpers 3 23.08%
I want a USB connection 2 15.38%
I want a serial connection (DB9) and Iíll use my own USB adapter 3 23.08%
I want a ICSP connection 3 23.08%
I want a premade parts list (BOM) at Digi-Key 2 15.38%
I want a premade project parts list (BOM) at Mouser 1 7.69%
I want 1 design and 1 design only 1 7.69%
I want optional designs to choose from and Ill make the boards myself 8 61.54%
Multiple Choice Poll. Voters: 13. You may not vote on this poll

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Old Sep 26, 2014, 07:57 PM
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Quote:
Chasing a small fault at the moment with the output oscillating just as the slot closes over the magnet when turning the disc slowly by hand.
Get normal spark when running but also get this occasional "multi-spark"
Sounds like the HV is retriggering on the induced voltage from the spark. I had the same problem, and its a bugger to fix. Cable routing and well grounded screening is required. I also added zeners to clamp the input lines to a fixed ceiling and tried RC filters

Pete
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Old Sep 26, 2014, 10:30 PM
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Joined Dec 2012
84 Posts
Whenever I encounter that double spark, I look at the bias resistor, the 680 ohm I use sometimes is too high for triggering the SCR. Try lower resistors or higher till it functions as expected. Let me know what works for you.

John
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Old Sep 27, 2014, 02:19 AM
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Pete,
I was about to start on the same route re-zener.
Reason was I included a power LED on the supply line and I notice supply dip when it fires.... initial thoughts were that re-triggering because of this might be the problem.

John,
Not sure which resistor you are referring to.......... no 680R anywhere in my system ...can you be a bit more specific....Thanks ...Jorgo
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Old Sep 27, 2014, 02:19 AM
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New Zealand
Joined Nov 2013
119 Posts
I must admit the clamping and filter circuits were Ray and myself having a flashback to our radar systems days.

Pete
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Old Sep 28, 2014, 06:00 PM
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Jeff, in my circuit that goes to the SCR gate there is a 680R in series with the .1uf cap. Reducing resistance sometimes helps if there's a trigger problem.

John
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Old Yesterday, 10:35 PM
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Joined Dec 2012
127 Posts
Problem with multiple firing on the basic (no micro- hv board) fixed.

I have the unit on bench test now, just firing an open plug i.e. not in an engine at this time.

Addition of zener, resistor and small cap did the job.

See attached drawing.
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Old Today, 01:20 AM
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Joined Jul 2014
48 Posts
Way to go BlueJets!

I never did hear back from the coil company rep that said he thought he could help us. But, development of the winder is going well. Feel free to join in on that...

It would help my understanding, if someone would take the schematic for the Gompy Timer Board B, latest version, that I posted at post #833 and tell me the functions for the three options that require jumpers and the components that are used in each option.

I have a basic understanding of what different electrical components do. I also understand the "big picture view" that components are selected for function and compatibility. I understand that some components are used to condition the circuit, for volts or amps. Other than that limited understanding, I can follow a schematic and solder things up. But, I have no skills to design a circuit. Maybe I will, one of these days...
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Old Today, 02:44 AM
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Joined Dec 2012
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The resistors (4k7) are there to hold a pin of the micro either high or low state.
Not good to leave the input floating as weird things can happen.

They can also be set in software i.e. pull-up , as far as I know.

Whether it is kept in a high or low state depends on what the programmer wants it to be.

When you see a large value cap like the 47uF and a small value cap (10 nano) it is usually to filter out noise.

I'd have to check the program to see what the jumpers do, but from memory I think one was for high or low kill switch, one was for magnet approaching the hall or leaving the hall for trigger ....can't remember last one.

Someone else will jump in here I'm sure...
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Old Today, 03:37 AM
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Joined Sep 2011
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Quote:
Originally Posted by bluejets View Post
They can also be set in software i.e. pull-up , as far as I know.

I'd have to check the program to see what the jumpers do, but from memory I think one was for high or low kill switch, one was for magnet approaching the hall or leaving the hall for trigger ....can't remember last one.

Someone else will jump in here I'm sure...
IIRC all the required internal pullups are enabled in the code. External pullups can't hurt and are often good design practice.

The jumpers are for kill switch and table select.

The A and B board versions were due to discussions on the best way to implement the kill switch. We wanted the kill switch to be reliable. The issue is that the kill switch could short out and prevent the engine from being killed. By requiring a high signal level, if the switch shorts out, or power is somehow lost, or the kill switch becomes disconnected then the engine is guaranteed to stop.

But if the switch wires become crossed (shorted together somewhere along the kill switch wire) then either board design will result in the kill switch not working. It's just more likely that something gets shorted to ground on accident.

The v1.0 code is written to have two switches attached. Kill and table select.

Here is the v1.0 video...
CDI-2012_v1.0 (2 min 0 sec)


I show the table select and kill switch functions in the video. The switch I had is labeled M and T.

IIRC "M" stands for momentary, and "T" stands for toggle. So the M is for the kill switch, and you have to hold it to activate the killing. The T is a two position switch and will stick up or down each time you press it.

You should always have a normal, manual kill switch that shorts the spark. Never rely on the firmware to sense and actually kill the engine when a digital switch is activated.

It would be pretty bizarre to have the PIC able to still fire the spark, but unable to shut down via the kill switch... but stranger things have happened.


-Jake
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Old Today, 03:54 AM
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Quick note... If you don't hear me talking in the video then you are listening to just the right channel of the audio. The left channel has my commentary.

Just watched it with one earpiece and couldn't hear anything but the engine... strange.

Also, we never really solved the problem of losing timing with the RPM. If you watch the video you can see that the advance lowers when the engine is revved.

It's not really a problem, and could be corrected out in the curve, but it is several degrees over the RPM range and is something that needs to be fixed.

The firmware code and timing is correct, so I still think it is from capacitance in the lines or circuit, or some sort of delay in the hall sensing.

My code is interrupt driven and the ISR service time is calculated out. So I think that the firmware is correctly timing the proper delay from when the hall is activated.

This means that either there is some delay in the hall circuit, or that the spreadsheet is somehow calculating the table wrong in a way that loses advance as RPM increases. I find the latter a bit harder to believe than the former.

Sadly, I'm not sure if the same problem happens in the newer OTF code. I tested it several times, but never actually looked for that same issue. The video just reminded me of it when I looked it up on youtube.

-Jake
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Old Today, 06:53 AM
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Joined Dec 2012
127 Posts
When chasing the multiple sparking with the HV board above, I had a neon type timing light connected in series with the HT to the plug.

I did notice a shift in timing there because of the noise at higher revs so just wondering if it might be along the same lines with the microcontroller version.

Something to try I guess.
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