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Topic: Sensors for quick detecting (Read 187 times) previous topic - next topic



So my project for the next 8 months involves building a steel target that detects when a panel has been hit by a bullet. The panel will swing on a hinge after the bullet makes contact. My question is what sensor do you think would be best for detecting this. I am trying to avoid placing any sensors on the panels themselves just in a bullet does deform the steel and damage the sensor but I'm not ruling it out completely.

I was thinking that a hall effect sensor would do the trick if I could magnetize the panels to keep them in place the hall sensor could work (in my head this seems logical). But I was wondering if there is a better option. I'm not trying to point out where exactly they hit on the panel just which panel they did hit.

I chose hall effect because there are going to be upwards of 20+ panels so I assumed if I'm using an Arduino that I need to use the digital pins on a mega or a due. Any other suggestions on sensors and does my idea for using hall effect sensors to detect the steel panel make sense?

Thank you,


Use accelerometers to pick up the motion.


What is your budget? Is it indoors or outside? This can effect the type of sensor required.

If it is outside you need it to be weatherproof so a sealed connector is required. This would allow sealed reed switch and magnet to be used.



A hall sensor seems a good option, but you have to attach a magnet to the panel. That will not be easy.
Perhaps with a coil and induction. Or a lever to the panel and a opto-switch or IR distance sensor. There are a number of ways to make it very strong and cheap.
Measuring the actual acceleration of the panel is best, but I think than an accelerometer is broken with the first bullet.
How is the construction of the panel with the hinge ? can you make a photo or a drawing of it ?

Why use a hinge ? If you attach the panel to a few very firm foam layers, it will be easier to measure the impact. For example EVA foam. Like this : panel --- thick foam --- plate with sensor --- thin foam --- solid base plate.
Or is it better if the panel can swing ?


Its for target practice and the person in charge wants instant feedback of where you hit so he wants the panels to swing. I am worried about accelerometers just because if there is any deformation to the panel the sensor could break.

So its not possible to use magnets on the frame to hold the panel in place, and having the hall sensor detect the steel panel being magnetized. I'm not the greatest when it comes to magnetic field but in my head it felt like that would work.

I will try and get a drawing for you. I'm in a bit of a rush at the moment.


Use accelerometers to pick up the motion.
I have worked a bit with accelerometers, the ones I worked with gave out an analog signal is it possible for them to be plugged into the digital pins?


I'm afraid an accelerometer will break. A digital input for an analog signal is possible, but most accelerometers are 3.3V and most Arduino boards are 5V.

How do you want to use a hall sensor without magnet ?
I don't want to use a magnet to hold the panel in place, but a magnet is needed for the hall sensor. It will be hard to glue the magnet firm to the panel, since the impact of a bullet is so big.


I would be surprised if the MEMS acceletometers would break, I worked for a defense contractor and I think you would be amazed at the shock MEMS sensors can withstand, they are hard to break.  To handle the 3.3V problem buy some 3.3V Pro Minis they are quite a bit cheaper than Arduino Unos and did I mention they operate at 3.3 V.  I buy them a dozen at a time they are so affordable.  We are all going to have to learn how to handle 3.3V sensors or we won't be able to sense much of anything as most new sensors are coming out at 3.3 V and fewer are 5 volt tolerant on inputs as in the past.

There are accelerometers that have digital output and some that have interrupt outputs if the total acceleration is over a user set threshold.  Your problem is not that hard it is done all the time at many gunranges.

Piezos epoxied to the steel will work also but you will have to do some signal conditioning to get digital output that is why I originally recommended accelerometers.

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