Lab Radar External Trigger

[alfsauve]

On another forum, THR, a user name Peels started a thread about Lab Radar and its external trigger.  Seems he found these "shake" switches which detect movement and could be used to trigger the LR.  I thought I'd experiment with this, not that I've had any problem with my LR.   I also used it as an excuse to buy a USB O'scope, a variable power supply and a cheap function generator for future experiments.

THE PROBLEM:   Lab Radar has to have a way to know when to look for your projectile down range.  By default it has a built in microphone which lets it know when you've fired.   Problem is two fold, a) silenced weapons, especially .22 rimfires and air guns may not produce enough "noise" and b) on very noisy ranges it can get confused as to which shot is yours.   

SOLUTION:  MyLabRadar sells a remote sensor, but it's $45.  A forum user, Peels, found some switches which detect motion and thought they could be used as a cheap alternative to the LR expensive remote microphone.  They're available for <$6 for 10. 


https://www.amazon.com/gp/product/B00UAFQW7U/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Here's what one of them looks like mounted to a 1/8" TRS (3.5mm) jack:



Since LR provide the necessary voltage you just solder the Shake switch across the ring and tip connections of the jack, use a 1/8" patch cable, secure your Shake switch to your gun and you have a solution to the problem. 

I took an old scope ring, cut it down and mounted my Shake switch to the ring with a plastic cable clamp.  Plug the 1/8" stereo (TRS) patch cable between the two and voila.







Here's what the signal the Shake switch produces when attached to an air soft pistol.



Now the LabRadar doesn't seem to mind this rather "dirty" looking signal and triggers just fine.  But I took a 10uF capacitor across the trigger signal to ground to provide some signal smoothing.   Here's picture of the Shake switch and the capacitor soldered to an 1/8" stereo (TRS) jack.




Now the signal out of switch contact is a little more reliable and  looks like this.





Wrapped both of these switches and their 1/8" jacks in several layers of heat shrink wrap.  Could just use tape, but this was neater for me.  Also discovered that orientation of the switch doesn't seem to affect it's detection. 





The Lab Radar has 8 levels of sensitivity settings.  If I were using an external microphone then it would make a difference in the detection level, but I'm just using a switch, so any of the middle level is just fine.    Going to take this all out to the range to test with actual firearms.  Probably a .22lr pistol and rifle and a 9mm pistol.    There could still be problems with guns that have virtually no recoil.  Maybe some PCPs or very heavy .22 rimfire single-shot guns.

[Rastus]

When I first looked at this thread back in whenever, I planned to look all this stuff up and see just what the heck you were talking about.   So I had the time to go beyond skimming today and I see what you were talking about. 

A shake (or vibration) switch seems to be a great solution if you have a problem with your unit.  At first I was wondering what the heck when I skimmed the article but now I see that Owon unit is a oscilloscope...so it made sense I somehow thought it was a radar unit. 

Speaking of which, I had no idea radar unit prices are in the affordable range.  I even see there are barrel mounted units for pellet guns and even units for bow and arrows.  Then there is a magnetic chronograph that straps to the barrel of your gun priced in between the radar unit and the skyscreens out there. 

So what do you think about that radar unit....?  I hate those old skyscreens and depending on the sun and clouds the readings can differ from week to week....so I think that radar unit would be fun.  I stopped bringing it to the range because of the skyscreens being a pain and people waiting on me to get them set up was uncool. 

And besides I probably can't buy paper for my chronograph anymore.

[alfsauve]

Rastus,

Lab Radar, and I'd guess there will be competing units at some point, is the cat's pajamas.  Just set it on the bench, point it towards your target and blast away.   So simple to use.  I don't regret for a moment spending the money on it.

Since you don't have to go downrange you can set it up at an indoor range or outdoors where you don't have to make the range safe in order to set it up and adjust it.   At one competition they had a trio of them for the chrono stage.  One left, one right and one low.  All pretty much had the same readings +/- a couple fps. 

I hadn't had any problem with my trigger but if you have people right next to you it could get confused. The shake switch was more of an experiment because someone over on THR had started down this path and I thought I could do it better.  But it's nice to know you have this ability. 

[Rastus]

Yeah, I guess it's time to put what I have on eBay and see if it goes.  I have a roll and a half of paper.  I can't even remember the name of it but it was top shelf when I bought it from someone on eBay 15 years ago or so. 

So what about that PC based oscilloscope you have?  I've been meaning to get an oscilloscope for my ham radio equipment....I may need a bit more bandwidth but I haven't really researched them yet. 

[alfsauve]

I got the Owon that you see pictured.  USB interface. Dual channel and comes with probes.  Not a real high frequency.   I think ~$100.  I've owned scopes in the past, this is as easy to set up as any.

But the absolute best piece of gear I got doing this was a variable lab power supply.  I've didn't realize how much I missed out on not having this.  So handy, especially now that I'm playing with Arduino projects.

[Sponsor]