DIY Chronograph

[seb]

I wanted a chronograph, but didn't want to pay for one so made one. Currently it's very prototype-y but if others would be interested in building one I'd be happy to polish the design a bit more. Currently just capturing the waveforms with my ocilloscope, and the detectors are giving high SNR even with .177 pellets.

It works by passing a pellet through some coils and detecting the change in inductance that results. I personally prefer this to the optical detectors. Maybe things have improved in the last several years but I always had such a hard time getting the lighting just right for those. These coils obviously do not care about lighting and have worked 100% of the time with 0 false triggers so far (only used for ~100 shots tho)

If anyone is interested in the design files LMK and I will post them!
Also curious if others have built something like this before, or if anyone has suggestions for improvements

 

[Treefrog]

That's cool! I have an E/E friend that would so dig on that.

I experimented a bit with using sound to get an average velocity a while back, but wasn't happy with the results.

Cheers,

J~

 

[beerthief]

I wanted a chronograph, but didn't want to pay for one so made one. Currently it's very prototype-y but if others would be interested in building one I'd be happy to polish the design a bit more. Currently just capturing the waveforms with my ocilloscope, and the detectors are giving high SNR even with .177 pellets.

It works by passing a pellet through some coils and detecting the change in inductance that results. I personally prefer this to the optical detectors. Maybe things have improved in the last several years but I always had such a hard time getting the lighting just right for those. These coils obviously do not care about lighting and have worked 100% of the time with 0 false triggers so far (only used for ~100 shots tho)

View attachment 476408

If anyone is interested in the design files LMK and I will post them!
Also curious if others have built something like this before, or if anyone has suggestions for improvements

I think this will be an exciting post . Maybe you should make a drawing and schematic and written explanation AND have a notary sign and date it , time also before you go any further .

 

[rikkochet]

I doubt if you will get a patent as it looks like a new version of an old idea (1940s).
Not holding that against you, though, and I hope you make a successful chronograph.

 

[beerthief]

I wanted a chronograph, but didn't want to pay for one so made one. Currently it's very prototype-y but if others would be interested in building one I'd be happy to polish the design a bit more. Currently just capturing the waveforms with my ocilloscope, and the detectors are giving high SNR even with .177 pellets.

It works by passing a pellet through some coils and detecting the change in inductance that results. I personally prefer this to the optical detectors. Maybe things have improved in the last several years but I always had such a hard time getting the lighting just right for those. These coils obviously do not care about lighting and have worked 100% of the time with 0 false triggers so far (only used for ~100 shots tho)

View attachment 476408

If anyone is interested in the design files LMK and I will post them!
Also curious if others have built something like this before, or if anyone has suggestions for improvements

I would still record this as an idea like i said in post #3 . I have had ideas borrowed from me and they are bringing home 6 figure salary's now .

 

[seb]

Thanks for the support! I think I would be very proud if someone thought this was a good enough idea to steal, so I will make it easy for them...

I would be interested how they did this in the 1940s. I ended up using a PLL and that seems pretty high tech for the 40s

Basically it works by having that large loop as part of an LC oscillator. Then a PLL is following that oscillator. When the pellet enters the coil the frequency slightly increases. In order to follow the oscillator the PLL increases it's control voltage. We then just amplify that control voltages and apply some rudimentary signal processing.

The only thing I am really proud of is the detector. It finds the peak of the waveform by looking for the first time it is above some threshold AND no longer increasing (using comparators and differentiator)

I am not really sure where to find a notary, but I will attach my schematics here (and gerbers too)
If you build this please be aware there were a couple bugs I had to fix with rework
- one comparator connection is reversed (U6A)
- the power for one opamp is reversed (U1)
- a fair few values are missing
I'm hoping I will make the effort to attach complete and working files at some point in the future

View attachment seb_chrony.pdf

View attachment gerbs.zip

 

[rc4fun]

Your bank will have a notary, and usually free for members.

 

[rcs9250]

Your bank will have a notary, and usually free for members.

Realtors and license bureaus too. Although license bureaus will sometimes only do vehicle titles.

 

[SilentSquirrel]

Thanks for the support! I think I would be very proud if someone thought this was a good enough idea to steal, so I will make it easy for them...

I would be interested how they did this in the 1940s. I ended up using a PLL and that seems pretty high tech for the 40s

Is the naivete incorporated in the design?

 

[rikkochet]

Sorry for the delay, my book was on loan to a friend.
It is in "The modern shotgun" by Burrard, Vol II. I have the 1955 edition, your library can get it.

The method was invented in the US by a man called Bradford in 1942 and improved on by Weller in 1952.
The US Patent Office will most likely have the details.
As far as I can tell from the diagram the coils are connected to an oscillator, the oscillator is connected to an amplifier, the amplifier is connected to a chronometer, and the chronometer is connected to the thigh bone.
Sorry, got carried away.

A chronometer shows time, not velocity, we did not have the luxury of chronographs then so had to use a pencil and paper. It worked.

 

[Extraclass]

Today you can buy one cheaper than the parts to build just about anything. I have just about give up on building gadgets. When m was looking for parts I found a Stereo 200 Watt audio amplifier under $10 built on a beautiful glass board with quick connects for input, output and power. Times are changing and the kids today are missing great learning opertunites!

 

[NateChrony]

I make chronographs - recently got into the industry... honestly its a horrible, horrible industry to be in

Awesome application, interesting that they did it back in the 40's/50's - yet Magneto have a current patent that covers... something?
Would this encroach on the existing magneto patent? if they stated sending you letters... got the money to defend? :/

If you could get the size down... could be very interesting... PM sent...

 

[oregondude]

I wanted a chronograph, but didn't want to pay for one so made one. Currently it's very prototype-y but if others would be interested in building one I'd be happy to polish the design a bit more. Currently just capturing the waveforms with my ocilloscope, and the detectors are giving high SNR even with .177 pellets.

It works by passing a pellet through some coils and detecting the change in inductance that results. I personally prefer this to the optical detectors. Maybe things have improved in the last several years but I always had such a hard time getting the lighting just right for those. These coils obviously do not care about lighting and have worked 100% of the time with 0 false triggers so far (only used for ~100 shots tho)

View attachment 476408

If anyone is interested in the design files LMK and I will post them!
Also curious if others have built something like this before, or if anyone has suggestions for improvements

Zero errors is the gold standard. I like. If you are OK giving away your work, so be it. However, if you're interested in possibly earning a few bucks, read on. Simply because someone did this in the 40s doesn't preclude a patent for your design. There are a myriad of products out there that serve the same purpose, but have their own patent. This is due to the patent application form section titled "Mode". This is where the applicant discusses what makes this device different from all others. There are several Patent Repositories scattered around the country that store patent information. Look for any product that seems to be like yours, and study the "Mode" portion. Next, do a little Google research on "Provisional Patents". You will likely file a "Utility Patent " ,but a "Design Patent " might be in play also. Hope you have whatever success you desire. Bill and Addi.

 

[seb]

Zero errors is the gold standard. I like. If you are OK giving away your work, so be it. However, if you're interested in possibly earning a few bucks, read on. Simply because someone did this in the 40s doesn't preclude a patent for your design. There are a myriad of products out there that serve the same purpose, but have their own patent. This is due to the patent application form section titled "Mode". This is where the applicant discusses what makes this device different from all others. There are several Patent Repositories scattered around the country that store patent information. Look for any product that seems to be like yours, and study the "Mode" portion. Next, do a little Google research on "Provisional Patents". You will likely file a "Utility Patent " ,but a "Design Patent " might be in play also. Hope you have whatever success you desire. Bill and Addi.

This is great information! Thank you

 

[Coxworkshop]

Very interesting. I had been working on a DIY chronograph that was integrated into a moderator. here I went the optical route. Ran that into a esp32 micro controller with a small screen. Some of the prototypes worked fantastic. Some didn't. It was infuriating. I made a couple custom PCBs and would configure prototypes exactly the same and then check them on the oscilloscope. Some worked some didn't. Something in the op amp or photo diodes wasn't consistent. Anyway like I said it was infuriating. I have one that works well for myself and figured I'd put the project to the side for now.

Sounds like your inductance method might be the ticket. Anyway if you want to use any of the esp32 integration that I've already worked out I'd be happy to send it your way. I'm a big fan of individuals making DIY stuff. Happy to share anything I've done if it looks helpful to you.

 

[NateChrony]

Very interesting. I had been working on a DIY chronograph that was integrated into a moderator. here I went the optical route. Ran that into a esp32 micro controller with a small screen. Some of the prototypes worked fantastic. Some didn't. It was infuriating. I made a couple custom PCBs and would configure prototypes exactly the same and then check them on the oscilloscope. Some worked some didn't. Something in the op amp or photo diodes wasn't consistent. Anyway like I said it was infuriating. I have one that works well for myself and figured I'd put the project to the side for now.

Sounds like your inductance method might be the ticket. Anyway if you want to use any of the esp32 integration that I've already worked out I'd be happy to send it your way. I'm a big fan of individuals making DIY stuff. Happy to share anything I've done if it looks helpful to you.

It took me a year to get my bugs out - i cant emphasize enough how hard it is to do the required measurements with the required precision.
Using a generic operating system/libraries will typically lead to tears, low level programming is really required with a real in depth knowledge of the underlying hardware behaviour etc. There are a LOT of workarounds required

 

[Coxworkshop]

It took me a year to get my bugs out - i cant emphasize enough how hard it is to do the required measurements with the required precision.
Using a generic operating system/libraries will typically lead to tears, low level programming is really required with a real in depth knowledge of the underlying hardware behaviour etc. There are a LOT of workarounds required

Definitely a hard problem but I wouldn't dissuade anyone from pursing it. Especially someone with a better background in circuitry design than me. My troubles weren't in the software side. The micro controller stuff is my bread and butter. That part was working fine. The issues I was having were definitely at the hardware level because I was able to measure them with the osciliscope before they even made it to the micro controller.