Author Topic: My transistor ignition and tachometer project (TigTac)  (Read 11138 times)

Offline PStechPaul

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My transistor ignition and tachometer project (TigTac)
« on: January 28, 2015, 08:15:06 AM »
I have finally started on this project, after much discussion elsewhere, and thought it should be in its own thread. I made a simple conventional ignition test board consisting of a 12V coil, points, and condenser, which I connected to a power supply, and was able to produce a spark in a spark plug. Here is a little video clip showing its operation - crude, but a start:

http://enginuitysystems.com/pix/TigTac_1707.AVI

I plan to make a cam for the points and have it turn with a crank, so that I can better simulate the conditions of a model engine. Then I'll make a better video and show more details.

Next step will be adding the simple electronic firing circuit as I showed in other threads. Here is the basic circuit and simulation:


Offline Don1966

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #1 on: January 28, 2015, 06:08:10 PM »
That's great Paul glad to see you getting started with it. I will be following along with great interest.

Don

Offline b.lindsey

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #2 on: January 28, 2015, 06:22:57 PM »
Paul, will the tachometer part be separate or will this one circuit fulfill both purposes?  I am particularly interested in a tach circuit I might could build, though I will leave the design to you guys who understand the sparky parts :)

Bill

Offline CHP

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #3 on: January 28, 2015, 08:47:50 PM »
Bill are you looking for an analog type RPM
or a digital one
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Offline b.lindsey

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #4 on: January 29, 2015, 01:01:03 AM »
Most things seem to be digital these days. Back in my high school years when I was still fooling around with model airplanes...Heathkit (remember them?) came out with a simple optical tach but the RPM readings were shown on an analog meter as I recall. It had a switch so that you could change between a couple of ranges of RPM's. Wish I still had it. I think the kit was about $20 back then but it had a nice metal case and such.

Bill

Offline CHP

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #5 on: January 29, 2015, 01:13:24 AM »
BILL if your answer is to me please specified what you are looking for
cheeras
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Offline b.lindsey

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #6 on: January 29, 2015, 01:21:41 AM »
CHP, my original comment was one of more general interest in Paul's circuit. I am not in serious need of a tach at the moment but if I was I would prefer it be digital. The thought of being able to make on as opposed to buying one has some appeal even if my expertise is far from circuitry design.

Bill

Offline PStechPaul

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #7 on: January 29, 2015, 01:34:37 AM »
This design should be able to function as a tach, spark generator, or both. It will be digital, but it is easy enough to add a filtered PWM output that can drive an analog meter, if desired. A fully analog tachometer operated from the points or cam position sensor is fairly easy to build, using a frequency-to-voltage converter.

Here is an inexpensive (under $2) IC that can be used as a tachometer as well as many other applications, and some circuit diagrams are supplied:

http://www.ti.com/lit/ds/symlink/lm2907-n.pdf
http://www.mouser.com/Search/Refine.aspx?Keyword=LM2907

Microchip has a more expensive ($8) device (TC9400) that can do both F-V and V-F conversions:

http://ww1.microchip.com/downloads/en/AppNotes/00795a.pdf
http://www.mouser.com/Search/Refine.aspx?Keyword=TC9400

Here is a simple circuit using a common 555 timer:
http://www.seekic.com/circuit_diagram/Automotive_Circuit/DISTRIBUTOR_POINT_TACHOMETER.html



Here's a compilation of many links for tachometers:

http://www.discovercircuits.com/T/tachometers.htm

Here's a very simple circuit using just one transistor:

http://josepino.com/circuits/?tachometer-circuit



HTH. Enjoy!

PS: Here is a sample of a digital version using a PIC18F452:

http://www.pyroelectro.com/tutorials/digital_tachometer_rpm/schematic.html


The choice of processor is rather arbitrary and only 12 I/O lines are needed, mostly to drive the LCD display. I plan to use a module that accepts the three I2C lines from the PIC so only one more is needed for measurement. I may also add a Bluetooth module to the RX/TX lines so that a handheld device or laptop can read and log the RPM data, and possibly also adjust timing parameters and other things.
« Last Edit: January 29, 2015, 01:42:38 AM by PStechPaul »

Offline PStechPaul

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #8 on: February 03, 2015, 06:54:27 AM »
Here is an updated working schematic for the TigTac. I just finished a marathon session getting the PIC16F1825 to drive the I2C connection to the parallel LCD display adapter, but it is finally working  :whoohoo: , although so far I only have it showing Hello on line 1 and Goodbye on line 2.


If you are interested, the files for the project are contained in this zipfile: http://enginuitysystems.com/files/TigTac/TigTac.zip

Offline PStechPaul

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #9 on: February 04, 2015, 06:37:34 AM »
Here is a video clip of the TigTac circuit showing dwell in mSec and RPM on a 16x2 LCD display. I am simulating the points closing and opening with a pushbutton switch on the PCB:

http://enginuitysystems.com/files/TigTac/TigTac_1709.AVI

I have updated the PIC files in the zipfile. I will be updating them as I go along:

http://enginuitysystems.com/files/TigTac/TigTac.zip

The I2C_PES.c and I2C_PES.h files are specific to the PIC16F1825 but may be modified for other PICs with a MSSP module for I2C. The LCD_PES.c and LCD_PES.h files work for the simple adapter I got for a couple dollars on eBay, and it should work for displays up to 20x4 and possibly 40x4.
http://www.ebay.com/itm/IIC-I2C-TWI-SPI-5VDIY-Serial-Interface-Board-Module-Port-Arduino-1602LCD-Display-/201097851956


Offline 90LX_Notch

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #10 on: February 04, 2015, 10:38:09 AM »
Paul-
This is very cool.  I wish I understood electronics;  it is totally foreign to me.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Don1966

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #11 on: February 04, 2015, 07:49:37 PM »
Nice job Paul and I do have a question. Did you make previsions to add a dwell and timing adjust? Like 10 turn pots to an analog input. It need to be flexable so you don't just have to program it to one particular engine.

Don

Offline PStechPaul

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #12 on: February 05, 2015, 01:32:16 AM »
I have not gotten that far, yet, but the finished product can have those adjustments. The dwell is really only needed for cam-actuated mechanical points, and all that is really needed is enough time to saturate the ignition coil primary, at which point it holds its maximum inductive energy and any longer just wastes power in its resistance and the external resistor (if needed). I have thought about this and there are a couple of ways to deal with it. Since it will have adjustable advance which will also vary with RPM, it will be necessary to sense one complete cycle of points closed and open to determine the RPM (and the time before next point opening). Then the software will need to wait until the time that corresponds to the next firing, which will be the time of one revolution less the advance time and the dwell time. At this point the coil will be energized for the dwell time, and then the primary will open at the advance time. As long as RPM does not change a whole lot between revolutions, this should work out pretty well.

The settings for dwell and advance might be done via Bluetooth or a display menu and one or more pushbuttons or a keypad. The advantage of Bluetooth or other communication protocol is the ability to do data logging, and perhaps make adjustments while the engine is running. I am a bit constrained by the 14 pins of this particular PIC device, but there are others with 20 and 28 pins that cost about the same, and there is really no need to conserve space.

For instance, the PIC18F14K22 has 20 pins and costs only about $2 (and I have a couple):
http://www.mouser.com/ProductDetail/Microchip-Technology/PIC18F14K22-I-P/?qs=sGAEpiMZZMsnNKdmhDfM1H%252bN4%252b417SNT

And the PIC16F1829 is the same family as the PIC16F1825 but has 20 pins and costs about $1.80 (and I also have some).
http://www.mouser.com/ProductDetail/Microchip-Technology/PIC16F1829-I-P/?qs=sGAEpiMZZMsyrc46HKMtR5TsJh015Vw1

The PIC18F24K22 is also about $2 and has 28 pins and many advanced features:
http://www.mouser.com/ProductDetail/Microchip-Technology/PIC18F24K22-I-SP/?qs=sGAEpiMZZMu9ReDVvI6ax%252bSchEKPtlU%252b65%2f8MwgJSsM%3d

I have some PIC18F2420 28 pin devices which are now a little more expensive but I would not need to order them.

Since the processor is so cheap I might as well use one of the larger ones and have plenty of elbow room for new peripherals and functions.

Offline Don1966

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #13 on: February 05, 2015, 02:01:18 AM »
Agree bud you need to program around a chip with more then you need, in case you need it. One thing that you need to consider to, is the cost of making the project. To get builders interested it has to be at a reasonable price and user friendly to the person installing it. Having external adjustments to trim the timing and dwell makes it more user friendly.
Keep in mind that we want the advance to be triggered by say any given speeds for any engine. Having an external adjust to trim this would also help setting up an engines advance because no two are the same.

The use of blue tooth and display s good for setting up and testing but what of the cost?

Don

Offline PStechPaul

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Re: My transistor ignition and tachometer project (TigTac)
« Reply #14 on: February 05, 2015, 03:01:35 AM »
You can get a Bluetooth HC-06 slave module for just $4 including shipping.
http://www.ebay.com/itm/HC-06-Slave-Bluetooth-Module-Wireless-Serial-Port-Module-Communicate-for-Arduino-/371221433944



The pins connect directly to the RX and TX lines of the processor, and pretty much any modern computer or tablet has a Bluetooth transceiver, or you can get a USB dongle for about $5. You can run a simple, free serial port terminal program like ProTerm or HyperTerm which comes with earlier versions of Windows. The PIC would need to listen to the incoming serial signals and interpret any commands that are sent from the terminal. And it can send data from the PIC indicating the RPM and dwell and other information. Instead of the terminal program, an application could be written with a nice GUI and controls for adjusting the parameters.

Thus the hardware for Bluetooth may be cheaper than a couple of trimpots and switches or keypad, and it could even eliminate the need for the LCD display. It's amazing how inexpensive these things are. Most of the expense is in the electronics design, programming, and making a PCB. Even that can be made for about $2-$5 in quantities of 20-50 pieces or more (from China, of course).

 

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