Labradar recoil trigger DIY

alfsauve · Nov 2, 2020

Thanks, Taff. That's what I have found with my field tests. I used the medium sensitivity and it worked fine with a heavy .22lr rifle, a .22 pistol and a Glock 9mm. As you said cocking did activate it but it worked fine with and without a capacitor.

Here's a picture of it mounted to my 10/22

Unfortunately, my 22/45 pistol has no rail, so I just taped it to the gun.

After all we're just detecting the recoil not trying to do any measurements.

Oh and on the G17 the recoil did tend to move my simple plastic clamp mount around. Not a big deal as the switch doesn't care about orientation.

SO: Thank you Peels and Taff for this fun side trip back into electronics. Thanks Peels for finding these switches.

Long story short: Do what Taff did. Just solder a shake switch across the tip and ring of an 1/8" stereo jack. Personally, i'd go for the medium sensitivity switch. Sensitivity settings don't matter for using the switch.

Taff · Nov 2, 2020

Al,

The idea of going straight off the switch/sensor without extra components is from one of the guys over on the 6.5Grendel forum. Prior to that I was using a capacitor and resistor thinking this is what was needed to smooth the trigger impulse, but not needed - the radar subordinates this to its 2 second delay.

This still works but the simplicity of just using the sensor by itself is obviously better.

Two methods of clamping specific to Picatinny rails;
A plastic rail cover
Cheap EBay bubble level.

More recently I just elastic band it to the scope or jam it in somewhere.

peels · Nov 2, 2020

Taff, where were you 3 months ago? Could have saved me some time!

As I said in my first post. Part of the fun was figuring things out. alfsauve just took it too another level! I appreciate you guys sharing and confirming my observations.

I concur. Using the shake switch straight up should be fine.

Taff · Nov 2, 2020

Peel,

Apologies, but I've only just joined and only because I stumbled across your thread.

Yes, the switch by itself and an elastic band works fine.

On a related topic and you guys might be able to advise me here. I use a Li-ion rechargeable external battery to power the radar. It is a 2S so 8.3V DC when fully charged down to 6V when the protection circuit kicks in. I currently use a voltage regulator to buck the voltage to 5V which is the standard for a USB port. I've been wondering whether the port would take the full 8.3V (without the regulator). I figure there must be some sort of internal voltage regulation as the battery compartment takes 6xAA batteries (assuming series = 9V).

I asked the sales rep a while back for the voltage range and he said it was confidential information. I had the impression he had no clue and was covering his pride.

Can I connect without the regulator? Is there a way to figure out the voltage range of the radar without destroying it?

alfsauve · Nov 3, 2020

Taff, 5V USB power packs are so cheap and plentiful, I wouldn't think it worth the effort to use something else.

While the internal battery pack of the LR might by 9V it could have it's own regulator to bring that down to 5V. The problem is that the micro-USB port might be downstream of that regulator. You could connect your 8V battery in place of the AA batteries and see if it works that way. That should be a low risk experiment. Wouldn't be hard to wire an external connector to the batter compartment if you want to keep using your 8V pack.

At the 2019 IRC they was running chronograph checks on a LabRadar that was powered by internal batteries. Of course it was on my turn that the readings were so far off everybody in line was shaking their head in disbelief. Fortunately, before the RO disqualified me, the LR screen flashed "low battery." After changing the batteries my ammo was retested and passed well above minimum PF. Point is there is a point below which LR will operate but will not give accurate readings.

Esok · Nov 3, 2020

Taff said:
Peel,
On a related topic and you guys might be able to advise me here. I use a Li-ion rechargeable external battery to power the radar. It is a 2S so 8.3V DC when fully charged down to 6V when the protection circuit kicks in. I currently use a voltage regulator to buck the voltage to 5V which is the standard for a USB port. I've been wondering whether the port would take the full 8.3V (without the regulator). I figure there must be some sort of internal voltage regulation as the battery compartment takes 6xAA batteries (assuming series = 9V).
View attachment 952977

It is not 9 volts.
Your assumption is wrong.
They split the 6 batteries 4.5v and wire in parallel so the voltage stays the same and the amperage goes up with more capacity.

Ask me how I know.
I purchased a new unit weeks ago and voided my warranty taking the tamper sticker off and opening it up for a update.

Hope this helps.

peels · Nov 4, 2020

Esok said:
I purchased a new unit weeks ago and voided my warranty taking the tamper sticker off and opening it up for a update.

Ok, I'm curious. What did you update that required opening up the unit?

alfsauve · Nov 4, 2020

Esok said:
It is not 9 volts.
Your assumption is wrong.
They split the 6 batteries 4.5v and wire in parallel so the voltage stays the same and the amperage goes up with more capacity. ....
Hope this helps.

That changes everything.

But again, USB power packs are so cheap and plentiful why mess with any other power source.

Taff · Nov 4, 2020

Esok,

Why did you open it up? What did you do?

Al,
Yes, USB battery packs are cheap and cheerful but I have plenty of spare 18650's and in this case 32650's. I shoot mostly at night when you have the range to yourself but you need lighting, hence the batteries. The 2S2P 10Ahr 7.2V pack was spare and now it powers the radar with a voltage regulator.

Esok · Nov 4, 2020

Nothing major.
I have never been a fan of the micro USB connection, they are cheap and flimsy and definitely not up to the task in my opinion.

I am installing a 5.5x2.5 jack and using a 5.5x2.5 / USB cord to be used with a 5 volt battery pack.
I plan on installing this bulkhead plug and soldering wires directly to the wire tabs on the unit.
It should be able to handle direct 5 volts as the 4.5 volts is only .5 volt difference .
This will replace the AA batteries.

igotbadbrains · Jan 29, 2021

Just to add some data. I used the above method to make a recoil sensor. The labradar mic was not 100% reliable when shooting my ruger precision 22lr suppressed. I'm using it to practice with my rangefinder linked to applied ballistic software and wind meter. So I needed good data to plug into my firing solution. EZ enough to make, but the medium sensor would not trigger for me. I had to go with the high sensitivity sensor to trigger reliably. I also ordered the wrong 3.5mm plug by mistake. It has to be a 3 pole stereo not two pole even though you are only going to use the tip and middle. 2 pole won't work. If your wondering what I made my case out of, it's a cap from the tube a BCG came in and one of those caps that come on the end of tipton cleaning rods. Strain relief salvaged from network cable. Just some 3m dual lock velcro to attach it. Epoxied the internals to help with false triggers. Works well. Thanks for doing all the hard work guys.

Clavdivs · Jan 30, 2021

You could use a monostable to debounce.
https://electronics.stackexchange.com/questions/271306/monostable-out-of-nand-gates
https://www.apogeeweb.net/circuitry/CD4011-cmos-nand-gate.html#cd4011-parameters

alfsauve · Jan 30, 2021

Clavdivs said:
You could use a monostable to debounce.

Trying to keep it as simple as practical. Or I could go the other direction and utilize an Arduino Micro programmable processor. Ooh. Wait. Hold my beer.

peels · Feb 1, 2021

Clavdivs said:
You could use a monostable to debounce.
https://electronics.stackexchange.com/questions/271306/monostable-out-of-nand-gates
https://www.apogeeweb.net/circuitry/CD4011-cmos-nand-gate.html#cd4011-parameters

Neat! I may try that if I get my hands on one of these chips. Thanks!

10 Ring Tao · Apr 8, 2021

Vibration/recoil trigger is where it's at, so for about $3 made my own. Whipped up the housing in Fusion 360 and then printed it, pulled a 3 pin aux cable out of a drawer, bought some vibration sensors, and voila.

Vibration sensors.

Cut off one end, strip to expose wires. The vibration sensor is tucked into the middle of the knot, showing the center post wire and thinner coil wire.

Testing fit in cavity.

Solder tiny f'ing wires to tiny f'ing wires. Test wires with a meter on continuity. The ring at the base of the plug is ground, figure out which wire is ground, cut it off. The other two are L and R (in my cord those were the red and white wires, yellow was ground), doesn't matter which solders to which on the sensor, because all it's doing is completing a circuit when the gun recoils.

Bend sensor wires down to the sides, wrap in electrical tape.

Apply heat shrink, put some glue/epoxy down in hole, stuff wires into hole, then cap off with epoxy putty.

Goes on any rail, cross bolt is common 8-32 cut to length.

peels · Apr 11, 2021

Nicely done 10 ring! :thumbup:

I did the same thing...but printed the pic rail mount in ninjaflex so I can just snap it on and off.

peels · Dec 31, 2021

Finally had some free time to play with a couple of 555 timers to setup the monostable trigger that @Clavdivs recommended above. I chose a resistor/capacitor combo that would give a 0.25 second trigger time. Figure that is plenty of time to hold the trigger voltage high to trigger the labradar while allowing the shake sensor to settle down. Once I got it all put together, the sensitive shake switch was able to trigger on very slight taps (even when moving it sometimes). The medium sensitivity shake switch appears to work much better than just using the switch alone.

But then I though....why stop here??

I decided to add an electret mic to the circuit (along with a LM393 comparator) so I can chrono my PCP air rifle also. The sound level to trigger can be adjusted via a potentiometer. I expect neighboring shooters to set off the sound based trigger at the range, so decided to added a simple slide switch so I can disable the sound based triggering in those situations.

Have not had a chance to try it out at the range yet, but was able to confirm the sound from a PCP is able to trigger properly. Dropping an AR bolt on an empty chamber also triggers nicely. Will probably have to wait for warmer weather before I will get a chance to test it out in the wild.

Taff · Feb 15, 2022

I use a 3.5mm socket to house the vibration switch. Same size as a AA so stows inside the battery compartment with its cable. I use an external battery so that compartment is where it stays.

Nothing fancy to attach it to the gun other than an elastic band.

thump_rrr · Feb 15, 2022

10 Ring Tao said:
Vibration/recoil trigger is where it's at, so for about $3 made my own. Whipped up the housing in Fusion 360 and then printed it, pulled a 3 pin aux cable out of a drawer, bought some vibration sensors, and voila.

Vibration sensors.

Cut off one end, strip to expose wires. The vibration sensor is tucked into the middle of the knot, showing the center post wire and thinner coil wire.

View attachment 990584

Testing fit in cavity.

View attachment 990585

Solder tiny f'ing wires to tiny f'ing wires. Test wires with a meter on continuity. The ring at the base of the plug is ground, figure out which wire is ground, cut it off. The other two are L and R (in my cord those were the red and white wires, yellow was ground), doesn't matter which solders to which on the sensor, because all it's doing is completing a circuit when the gun recoils.

View attachment 990586

Bend sensor wires down to the sides, wrap in electrical tape.

View attachment 990587

Apply heat shrink, put some glue/epoxy down in hole, stuff wires into hole, then cap off with epoxy putty.

View attachment 990588

Goes on any rail, cross bolt is common 8-32 cut to length.

View attachment 990589

View attachment 990590

@10 Ring Tao
Would you mind sharing the file for your housing?

Walkalong · Feb 15, 2022

Y'all are just too smart folks, super stuff.

DukeConnor · Feb 15, 2022

Being electronically challegened, we bought one for 35 bucks and attach it with a rubber band.

We do a lot of suppressed shooting and found it necessary to get reliable results.

The downside of the store bought one is it will trip when a bolt action is cycled.

alfsauve · Feb 15, 2022

Taff said:
I use a 3.5mm socket to house the vibration switch. Same size as a AA so stows inside the battery compartment with its cable.

<--- I am unworthy

What a very neat idea. I bow to you sir.

Taff · Feb 17, 2022

Thanks Alf, but to be fair the same size as a AA was just luck.

Duke,
The false firing thing is something we all have to live with. I just ignore it and carry on cranking that bolt like a one-arm bandit at a casino. The radar keeps giving that message screen that it can't see a bullet and to press a button to reset, I ignore it. Just carry on shooting and it will reset itself. I don't even know why they have it.

lordpaxman · Feb 18, 2022

DukeConnor said:
Being electronically challegened, we bought one for 35 bucks and attach it with a rubber band.
The downside of the store bought one is it will trip when a bolt action is cycled.

Do you mind sharing where you got it from?

DukeConnor · Feb 19, 2022

lordpaxman said:
Do you mind sharing where you got it from?

i don't remember. might have been amazon. its been a couple years.

Labradar recoil trigger DIY

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