Due to a few request I decided to make some improvements over my original version of this sensor.
The major improvements are a new 3 PCB design, which makes this much more durable than the previous version. The other huge improvement is using the Honeywell SD5600 Optoschmitt Detector which has a fall time of 15 ns. Previously I was using a standard photo transistor which had a response time of 15 us. This new design is 1000x faster! This actually matters on faster bullets since sometimes the old sensor wouldn’t notice a fast small bullet. The SD5600 never misses.
The only downside to this new design is that it’s a little more expensive. Here’s the BOM.
2x 90 Degree Male Header
2x 3.5mm Jacks
2x IR Emitters
2x Honeywell SD5600
2x 1K Resistor
2x Male/Male 3.5 mm Cable
This sensor has two IR sensors spaced exactly two inches apart. The user inputs the distance from the sensor to the desired position of the projectile when the picture is taken. Based on the time it takes the projectile to travel those two inches between the sensors, a velocity for the projectile can be determined. Since bullets and other projectiles basically travel at a constant velocity, it is easy for the microcontroller to calculate the delay in microseconds until the picture is taken.
Here’s a link to the Eagle files I used to create the PCBs.
Using the Projectile Sensor with the Camera Axe
There are 3 PCBs and everything is labeled so it’s supper easy to plug them together. You will need the 3.0.04 or newer version of the Camera Axe software. Turn on the Camera Axe and hit menu until you get to the projectile menu. Set the distance you want the bullet to be from the second gate when the picture is taken and then push the right button until you get to the “Trigger on” menu for the projectile sensor and set this to low. Now hit the set button. If the sensor continuously displays the speed of the projectile that means the sensor boards aren’t lined up correctly. Look at it from the side and bend the boards so the emitter is pointed directly at the detectors. Once it’s sitting there waiting for a projectile put your finger through the two sensors and it will report back to you the speed of your finger. Once you get this it’s working.
Mounting the Projectile Sensor
I mounted a projectile sensor to my pellet gun and it is working great. The pellet’s velocity ranges from 985 feet/second to 1060 feet/second. Below are a bunch of pictures of how I did this mounting.
Back when I started needing a way to organize my circuit designs on something more permanent than a breadboard I used wire wrapping. This was probably only 10 years ago so wire wrapping was and still is rarely used, but I liked it. It got what I needed done in an easy and fairly durable way.
Over the past few years I’ve wanted nicer circuit boards for my personal projects. There are many ways to make your own circuit boards at home. I’m sure there are over 100 articles on hackaday explaining the various methods. I’ve never done this. It seems like a lot of work to make the circuit board and then drill it out. Plus when it’s done it’s missing the useful solder and stencil masks. The obvious advantage to doing it yourself is you don’t have to wait for it to get shipped back to you which tends to take 2-4 weeks unless you pay big $$$ to expedite the order.
A few years ago I ordered my first few circuit boards from Batch PCB. They are probably still the cheapest place to get single boards made. The way Batch PCB works is to batch up individual orders and then send a big order to Gold Phoenix. It takes them a few days to batch up the orders. A few days to cut the boards once they get them back from Gold Phoenix and an extra week of shipping. So this means it usually took about a month from when I ordered until when I got the order. Besides the longer order time the price was expensive as soon as you started ordering more than one or two boards.
Next I started placing orders directly to Gold Phoenix. If you start selling kits like I do they are a great supplier and I’ve been very happy with them. I always order 155 sq inches of PCBs from them. They have options for panelizing, but I never tried that since I’m usually ordering PCBs for kits. 155 sq inches of PCB usually costs $100-140 depending on the options I choose. I’ve gotten anywhere from 15 to 100 boards from this 155 sq inches depending on the PCB size. I’ve also found that if I need to order more boards they give me a decent discount. I’ve had cases when ordering more boards that they cut the cost to less than half the advertised price. I’ve gotten 1000s of PCBs from Gold Phoenix and haven’t had a bad one yet. The main thing I didn’t like about Gold Phoenix was that you sent them your Gerber files as a zip file in an email and then had to pay for it through the Paypal site. The delivery time was about 2 weeks from when I ordered which is a little faster than their website says.
Some of the PCBs I’ve ordered from Gold Phoenix.
About a month ago I found a new PCB manufacturer call PCBWing. I’ve only ordered one batch of PCBs from them, but they had the same great quality as Gold Phoenix. Their website was much nicer than Gold Phoenix since it had much more flexibility on order sizes and a nice a shopping cart that let you pay for your order right on the site. I feel their website cuts ordering time in half compared to Gold Phoenix. Most single boards would still be cheaper through BatchPCB, but they have the cheapest prices I’ve seen on the web for small(5) to larger(100s) quantities of PCBs. For instance I found when ordering 100 3″x4″ PCBs PCBWing’s normal advertised price is still about half the secret discounted price I could get from Gold Phoenix. After I submitted my first order, I emailed some suggestions to PCBWing on how they could streamline their online ordering even more and they implemented the ideas in 3 days. That’s amazing service and the reason I decided to write this blog post. Basically I think PCBWing is a great new PCB manufacturer and I think people who order PCBs online should consider them as an option.
The first prototype of a new version of my Camera Axe
project. Don’t mind those blue wires. I added those to work around some bugs I made in designing this prototype.
That said there are a lot of PCB manufactures I haven’t tried and maybe some of them are great too. Ladyada has assembled a pretty good list here. Maybe she’ll add PCBWing soon.