Tachometer Help From MouseWheels?

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mousewheels
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Re: Tachometer Help From MouseWheels?

Post by mousewheels »

-- Calibration ---
Did you try playing with the pot to see whether it changes 0 or slope?
I wrote the pot off to slope - all resistors are 5%, but verified as slope tonight.
Is there a chance I can recalibrate mine? This of course assumes I have the patience and dexterity to pop the can lid off without mangling contents within. I'm guessing the "Trim" isn't going to compensate for the 50% value I'm seeing, but maybe?
Give it a try. Cal range on mine is wide. If it won't cal you can have the PCB from my bindy tach. PCB will ship for a couple stamps.
KEGE_Tachometer_Calibration_Range.jpg
KEGE_Tachometer_Calibration_Range.jpg (68.37 KiB) Viewed 7853 times
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Re: Tachometer Help From MouseWheels?

Post by mousewheels »

>> This guys selling cp1005 chips 10 for $11. Maybe he has a datasheet?
Thanks ng - Question to eBay seller is sent.

>> Here we go... Its an optocoupler. That makes sense in this usage... But would also imply that the whole thing is a simple circuit. No brains.
Yes - that would fit the low cost build.

>>Thought manufacturer was ICF. Perhaps ICP... And that means generic in Chinese?
Interesting and thanks - will look at the links for datasheets.
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Re: Tachometer Help From MouseWheels?

Post by Wheelman-111 »

Greetings:

Quoth MouseWheels the Magnificent:
Give it a try. Cal range on mine is wide. If it won't cal you can have the PCB from my bindy tach. PCB will ship for a couple stamps.
Thet-thar's a very kind offer. Any hints on what kinda can-opener to use? Also what the heck's a PCB? Para-Dichlorobenzene? Uncle Sam will have a cow if'n you put that in a mailer. Also remember Wheelman soldering "Skills" are sad.
I'll monkey with the calibrator, limited hope because of the way I had to wire mine - internal crossed connection?
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Re: Tachometer Help From MouseWheels?

Post by mousewheels »

Any hints on what kinda can-opener to use?
I used a 1/8" flat blade screwdriver on the first trips around the meter to get started, then a 3/16 or 1/4". Insert, twist, step and repeat. After the bezel looked straightened, I slipped the 1/8" blade past the case flange and popped the top off like a tire change.

> Para-Dichlorobenzene?
Moth balls in a tach? :)

> Also remember Wheelman soldering "Skills" are sad.
No problem - Easy access and 2 wires:
Tach_PCB.jpg
Tach_PCB.jpg (122.41 KiB) Viewed 7846 times
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Re: Tachometer Help From MouseWheels?

Post by noiseguy »

You know, another option would be to drill the shell to get access to that pot. Would ruin the weather seal unless you capped it up when done, and you'd need to know where to drill.

I've pulled this type of shell apart as well. It's like removing a tire... a little at a time. You can re-assemble pretty much the same way, though a blunt round object (like a large-ish drift punch) works best for smoothing it out. Otherwise use a wide-blade screwdriver and push the flange back down, 12:00, 6:00, 3:00 and 9:00 then working your way around the circle.

MW: Here's a simple tach circuit. Frequency to Current conversion. Not that up on circuit design but expect the optocoupler (if that's what it is) is the front section, there is no zero, and the high power available to move the needle on this device removes the need for the transistor stage. The only thing I don't see on the China tach is a bridge rectifier... perhaps they use the one diode on the board for some sort of clipping...

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Re: Tachometer Help From MouseWheels?

Post by paulpauly7 »

What do you two do as a day job ? This electronic stuff is right up you alley .Im learning as i go and starting a course soon on electronics mostly auto electronics
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Re: Tachometer Help From MouseWheels?

Post by Wheelman-111 »

Greetings:

Both Mighty Mouse and Noisy have the knowledge I would have gotten had I paid attention in Physics Class. A grateful tip of the Wheel-hat to you both.
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Re: Tachometer Help From MouseWheels?

Post by mousewheels »

>> NG: MW: Here's a simple tach circuit. Frequency to Current conversion.
Thanks - these day's it's still amazing to see how IC's took over simple circuits. One thing about the converter shown, is there are 3 adjustment pots. Those cost more than anything but the meter, then they incur costs calibrating them.

While searching I ran into a 50 year old Corvair tach circuit. It's simple and adds regulation of the 12v input (VR1). I'd guess the Corvair circuit remains cheaper than KEGE design 8) , however, it likely needs some changes to use with our scooter pickups. Also KEGE likely spent a good deal of effort to make the design low cost - so take it as arm chair observations...
Corvair_Tachometer.JPG
Corvair_Tachometer.JPG (57.3 KiB) Viewed 7821 times
The circuit is easy to simplify and describe in non-tech terms

The pic below replaces input trigger circuitry. It represents that as a switch
There are only two states
  • State 1: Charge ---> When switch is open,
    Capacitor C2 is filled with a controlled 'bucket' of charge, where VR1 regulates how full, and the value of C2 is the bucket's capacity
  • State 2: Measure ---> When switch is closed
    "Bucket' C2 is emptied into the river of current.
    At the designed full scale RPM ( we'll assume 8000 RPM), 8000 buckets/minute results in an average flow of 1mA, moving the meter to full scale
At intermediate RPM, the average flow is proportional to input RPM. Thus 4000 RPM = 0.5mA, 2000 RPM = 0.25 mA etc.
Corvair_Tach_Measurement_Portion_of_Circuit.jpg
Corvair_Tach_Measurement_Portion_of_Circuit.jpg (76.75 KiB) Viewed 7821 times
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Re: Tachometer Help From MouseWheels?

Post by mousewheels »

<paulpaully7>What do you two do as a day job ? This electronic stuff is right up you alley .Im learning as i go and starting a course soon on electronics mostly auto electronics
> Good to hear - count on fun and rewards :thumbsup: In the past I worked in electronic design.

--- Re: Integrated Circuit "'ICF CP1005"
Putting NG's links through Google translate shows evidence the CP1005 from ICF is described as a tachometer chip. See composite of two web pages below. The eBay seller thus far has been a no-responder for technical chip info. Also, I have partially traced the circuit board, but don't yet have a diagram to post.
ICF_CP1005_Chip_description_composite.jpg
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Re: Tachometer Help From MouseWheels?

Post by noiseguy »

Nice find on the Corvair circuit. I figured the design was basically "fill the cap with power then measure" but I didn't understand how the transistor played a part in that. Thanks for the explanation. The one I posted... R3 is zero, R4 and R2 work in combination to set the slope. http://www.circuitstoday.com/tachometer-circuit. If you are building into a gauge it would just be cheaper to design zero in, get slope close and leave one pot for calibration.

Yep... just easier and cheaper to plant one of these chips on the board and draw up the traces than to actually do a circuit level design. Probably cheaper to build, and I expect that the folks they have designing these are cheaper as well... less skill required in circuit design if you just use a chip along with the manufacturer's suggested design circuit.

Pauly: My background is in mechanical engineering. Electric circuit design was a hobby when I was younger, and I still dabble a bit now and then.
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Re: Tachometer Help From MouseWheels?

Post by cancunia »

Am thinking about getting a tacho and came across this thread. Just wondered, has anyone tried a digital tacho like this one?

http://www.ebay.co.uk/itm/Motorcycle-Re ... 1672381290?
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Re: Tachometer Help From MouseWheels?

Post by Meatball »

A popular choice is this one... https://scooterswapshop.com/collections ... tachometer

There certainly are many options out there besides this one but its small, compact and has all the parts you need to install. The one you posted needs additional wires and is rather bulky..in my opinion.
I need to find some new haters...the ones I have are starting to like me.
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Re: Tachometer Help From MouseWheels?

Post by cancunia »

Meatball wrote:A popular choice is this one... https://scooterswapshop.com/collections ... tachometer

There certainly are many options out there besides this one but its small, compact and has all the parts you need to install. The one you posted needs additional wires and is rather bulky..in my opinion.
Can't deny the one I found is not exactly a design classic, but somehow I thought it fitted that awkward analog / digital 80's crossover thing. Point taken about the wiring though and totally agree. Yours looks really cool, but for me is a bit too expensive as I'm only looking for a short term idea of what my top revs are.

I've ordered one of these, should do what I need:
http://www.ebay.co.uk/itm/Universal-LCD ... 2314631023
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Re: Tachometer Help From MouseWheels?

Post by Cagiva4ever »

old topic, but i have liked it....found this topic about 2years ago. i have now Actually same RPM tacho as "Kege" , but mine is integrated in a Tacho cluster at/from 4t 139QMB scooter. i bought the tatty Tachos alone so that i could take out the RPM tacho alone and make a Casing for it (by Lathe etc).

ive also seen a same r.p.m Unit but with 2-wires. where as "Kege" has 3-wire and also mine 3-wire.
i have pcb photos from this 2-wire version.

anyway, i noticed that my pcb is using different IC than cp1005. i shall post it up later....
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