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  #1  
Old 07-11-2017, 02:28 AM
HO RacePro HO RacePro is offline
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Default Inexpensive Droking Lap Counter

I have received two Droking counters, purchased on Amazon for US$15.12 each.

Short version -- they work! They really do work, and I believe they are an excellent option for someone looking for an inexpensive but reliable lap counter.

One downside. The magnetic sensor that comes with these units does NOT seem to be sensitive enough to detect HO slotcars. They may be sensitive enough for larger-scale cars with traction magnets.

However, used with a dead strip these units work great. I did end up adding a teeny-tiny capacitor* to 'de-bounce' the signal from the dead strip. A suitable cap will cost nearly nothing, and be dirt simple to install.



I've run tests to make sure these units are reliable.

My first test was to hook up a Droking in parallel with my TrikTrax lap counter. The Droking saw the same momentary contact when the car crossed the dead strip on my banked oval that the TrikTrax saw.



Both counters stayed in synch for 5,000 laps. I felt that was enough to be convincing.







But the Droking's response seemed to lag the TrikTrak by a fraction of a second, which said to me that the TrikTrax was 'loading' the circuit, probably with a capacitor on its input.

So my next test was to run the Droking with its own dead strip, completely separate from the TrikTrax. Said dead strip was kludged together out of strips of scrap phosphor-bronze I had lying around. As you can see they were laid right next to the track's braids, but not actually in contact with them.



The reason this dead strip worked was because my car had a Slide Guide installed. The Pickup Wires of the Slide Guide spread wide enough to contact the dead strip as well as the track's braids.



I did have to add that tiny capacitor to 'de-bounce' the input. But once that was done the setup ran reliably.

Here is a short video from that test.



And another video in slow-motion. Notice the car bounces a bit going over the dead strip. Despite that, the count stayed accurate.



That test ran to more than 2,000 laps. Again, the Droking and the TrikTrax lap counters stayed in sync.

Conclusion? The Droking counters should be on your short list of lap counter solutions.

Ed Bianchi

* No, I don't know the value of that capacitor. I just happened to have it laying around. Obviously it is a very small capacitor. Also obviously it is NOT an electrolytic capacitor -- so it does not have a polarity. That's all I can tell you right now.

Last edited by HO RacePro; 07-15-2017 at 08:03 AM. Reason: Removing Amazon link per Rule 13.
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Old 07-11-2017, 07:39 AM
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RichD RichD is offline
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The capacitors that come with Scalextric 1/32nd motors look to be similar, I will send you some of those and you can see if they work. People with regular plastic tracks could also use magnetic reed switches. You have to choose the right ones if you run pancake cars and cars with closed can motors would not count unless they also had traction magnets.
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Old 07-12-2017, 02:32 PM
Speedynh Speedynh is offline
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it's a little ceramic cap. does it have any numbers on it? first two would be the value, the third the multiplier, in picoFarads. i.e., a 471 would be 470 pF.
I'd say probably around a few tens to a few hundred puff at best in that size package. and since it suppressed your spikes, I'd say on the upper end of that range, but I'm guessing. either way, there ain't no stinkin' microFarads in that size, of that type.
I've got a million of 'em. they're like 1/4 Watt resistors. and they're not known for being stable, long-lived components. the bigger, fatter ones are called "Mexican Lollypops". guess where they were made.

(I shouldn't even ask this- did you put a 'scope on it to look at the waveform? lol)
speed
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Old 07-14-2017, 04:53 AM
HO RacePro HO RacePro is offline
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No, no numbers. That was the first thing I checked.

And yes, I once had a 'silly scope. Big ugly refugee from the 1950's (my guess). Had a cathode ray tube maybe 4 or 5 inches in diameter. Got tired of it taking up space and got rid of it a decade or two ago.

Short answer -- I suspect almost any small cap will do the job. I might do a few tests to see how small, and whether a larger cap might give a desirable amount of delay before the counter can be tripped again. That can be helpful in preventing extra lap counts in the event of 'riders'.

Ed Bianchi
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Old 07-14-2017, 07:11 AM
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The caps that I sent are marked 103M, you should have them soon.
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Old 07-15-2017, 10:56 AM
HO RacePro HO RacePro is offline
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Rich,

Thanks for sending me those three capacitors. I tried one, and it appears to work just fine -- no different from my unknown-valued capacitor.

They are marked '103M', which, according an online conversion app, is a value of 0.01 microfarads or 10,000 picofarads.

http://www.davidswinscoe.com/electro...itorscode.html

I suspect that there is a wide range of capacitors that would work, but now at least we know one value that DOES work.

Thanks again,
Ed Bianchi
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Old 07-15-2017, 03:48 PM
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will any of the exsisting race programs work with this?

Thanks, Harry
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Old 07-15-2017, 06:58 PM
Speedynh Speedynh is offline
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103M sure sounds like 10kpF to me. the M might be Mexico.
.01's are a commonly used value to suppress spikes, depending on their quality. - .1's are a little slow for high frequency RFI and .01's a bit small for anything less than about 50MHz. the ringy-dingies that you have are likely around 20MHz, so this is a good value, a good compromise between enough capacitance to do the job and small enough parasitic inductance so that it's not swamped by its own resonance at the frequency of interest.

(but gee's- you threw away a perfectly good working 'scope just because it was old and taking up valuable bench space? I would'a put it on the shelf or in the attic or something so you'd have it for a rainy day. not everybody's got something like that, and now you got nuttin'!)

glad it worked, though, and thanks to Rich for sending you something good.
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Old 07-16-2017, 07:44 AM
HO RacePro HO RacePro is offline
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Harry, if you are going to use a race program -- by which I think you mean a computer-based race management program -- discreet counters like the Droking would be superfluous. A race management program does lap counting, lap timing, lap statistics, and other nifty things.

You go to discreet counters like the Droking only because they are cheap, simple and reliable.

You go to race management programs for their whiz-bang features, and because you are able to cover their cost and put up with their computer-based foibles.

For many hobbyists discreet lap counters like the Droking should be affordable, and do all that is needed. If your needs are (or become) more than simple lap counting, then a computer-based race management program is your next step up.

My own preference is to stay simple. It works for me.

Ed Bianchi
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