The electronics

Laserontroller und Filterfolie The task of the electronics is to control the laser. This has to flash briefly when the trigger is pressed. Here, the time period is between 10 and 200 milliseconds and depends on the brightness of the laser as well as the sensitivity and frame rate of the camera. The shorter the laser can be pulsed, the better.

A small microcontroller circuit has been designed, which carries out this task. As there were many enquiries about this, a small batch has been produced so that the laser controllers can be ordered at any time. The price is € 10 per piece (EU shipping included). A piece of colour filter foil is enclosed with every laser controller. In the contact page you will find instructions for placing an order.

The Projekt ARES laser controller is an electronic control unit, which enables any technically skilled person to construct a laser gun or a laser rifle for his or her own shooting gallery. The electronic control unit evaluates the trigger activity and controls the laser. It is compatible with any suitable laser module, switch and battery so that all possible options are available for the construction of the laser gun. All details as well as some tips for the construction of a laser gun can be found in the instruction manual.

LasercontrollerEn.pdf instruction manual for the laser controller (4 pages, 0.4 MB)

The wiring of the laser controller can be seen in the picture below. If an infrared laser is used, a clearly visible LED warning light should be connected in parallel to the laser. Otherwise you cannot see if the infrared laser is in operation as it is not visible.

Schaltplan Laserpistole

The problem could also be solved with an analogue circuit or a discrete digital circuit, however, the use of the microcontroller has a lot of advantages. On the one hand the circuit is very small and robust and on the other hand it can be configured easily and further functions can be added. For example, the laser remains switched on if the trigger is held down when the electronics is switched on. This is very helpful for the testing of the laser detection and the calibration. Furthermore, in this mode you can adjust the length of the laser pulses by pressing the trigger several times.

The camera

Schießkino Webcam Any webcam can be used. Above all, a high frame rate is important. The camera should have a frame rate of at least 25 pictures per second. All new webcams have at least this frame rate. However, tests during the development of ARES showed that some (very cheap) webcams send some pictures several times so that they appear to have a high frame rate. It is important that the colour filter can be fixed easily on the camera. You have to find a way to mount the filter which allows it to be fastened on or removed from the camera without moving the camera. Simple filter foils such as those used in the theatre are very good. An overhead transparency marked with a permanent marker can also be used for the testing of the basic function but this cannot be recommended for the real operation. In general, the permeable part of the filter should match the wavelength of the laser well, whereas other wavelengths should be eliminated by the filter as much as possible. A piece of filter foil, which is optimized for red lasers, is enclosed with every laser controller bought.

With the Philips SPC100NC camera we have had the best results so far. It has a good frame rate and gives a sharp picture. It was easy to fix the colour filter on the big lens. For this purpose an O-ring was stretched over the lens and with this a small wire stirrup made from a paper clip was held in place. Then a piece of filter foil was wrapped around the wire stirrup and fixed with two staples. This simple and cheap solution works perfectly. The camera was bought in 2010. Therefore, this model may well not be available anymore. The PlayStation Eye can also be highly recommended. It is cheap and has a very high frame rate.

If you want to operate ARES with an infrared laser, you need a camera which detects it. In general, all image sensors which are fitted in webcams can pick up the infrared light generated by commercial infrared laser modules (wavelength about 780 nm). However, as it is this light which is not wanted in usual use, all webcams have a filter that filters out this light. There are some webcams where this filter can be removed. Unfortunately, you can only see whether this is possible when you open the camera. If you want to operate ARES with an infrared laser, you have to find a camera from which the infrared filter can be removed. The filter which is fixed in front of the camera during operation has to filter out all light apart from the infrared light of the laser. Mostly this can be achieved if you put a red and a blue filter foil on top of each other. However, you have to make sure that both of them allow the infrared light to pass.

The mechanics of the laser pistol

An airsoft gun is recommended for the construction of a laser waepon for ARES. These guns are relatively cheap, can easily be disassembled and have enough space for the electronics. How easily an airsoft gun can be converted into a laser weapon depends on the model and, unfortunately, can often not be seen before disassembling. In general the use of an electrical driven airsoft gun (also called AEG – Automatic Electric Gun) is recommended as this has a switch which can be pressed through the trigger, which can be used directly for triggering the laser pulse. A spring-powered airsoft gun can also be converted for use with ARES, however, it can, above all, be difficult to fit a switch.

The general method for converting the weapon is the same for all airsoft guns. The pistol is opened and analysed thoroughly. Commencing work too hastily is often regretted. You have to plan thoroughly how the necessary parts are fixed in the casing. These are the laser, the electronic control unit, batteries, a pushbutton for the laser pulse as well as an on-off switch. Therefore, some parts of the original mechanics of the airsoft gun have, of course, to be removed. However, some parts can be adapted for the new purpose. Parts of the gun barrel can often be used to fix the laser on it. The laser has to be placed exactly in this position in order to send its beam trough the muzzle. The laser should be fitted in such a way that it can be adjusted. The mechanics of the trigger can often be used to press the pushbutton for the laser pulse. When you insert the battery holder, you have to consider that the batteries have to be changed from time to time. However, as the electronics use very little power and the laser only emits light very briefly, you can play for about 100 hours with one set of batteries.

Laserpistole With the converting of the CM.030 electric airsoft pistol from the producer CYMA (see photo) we achieved the best results. This relatively high quality airsoft can be bought for about € 55 and is very suitable. The upper part can be removed easily so that you can change the batteries, which we placed there, fast and without tools. In this way the laser can also be adjusted easily. The existing switch, which can be activated via the gun trigger, was used in order to trigger the laser pulse. Here, springs generate good back pressure when the trigger is operated. The good workmanship of the airsoft is still evident after reassembling. The pistol is very handy and is a nice weight. The plastic material appears to be of high quality and the parts do not rattle when you shake the pistol. As the on-off switch a reed relay (magnetic switch) was fixed inside the pistol. This relay is operated through a magnet, which is glued in the magazine. The laser pistol is switched on when the magazine is inserted and switched off again when the magazine is ejected.

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