One Of The First Uses Of Mass Produced PCBs
Amongst the very first uses of mass produced printed circuit boards was the lesser known proximity fuze. A generic fuze is the part of an electronic device that makes it function. Eg. On a stick of dynamite, it’d be the fuse burning down to trigger the device. This device was perhaps lesser known due to the level of secrecy around the device during the war. This effectively demonstrated the versatility and effectiveness of the electronic printed circuit board. In 1948, the american authorities ruled all electronic circuits for airborne instruments must be printed. This proved its use and was one of the first steps in establishing the printed circuit board in almost every electronic device today.
The Proximity Fuze
The proximity fuze was developed to trigger when in close proximity or distance to its intended target. This distance was defined by a certain value, which when the distance was less than it – it was triggered. This type of device was incorporated into bombs or missiles for use against planes, missiles, ships and ground forces. The device was said to be one of the most technological innovations of World War II. This was due to it’s greatly increased effectiveness against targets versus the older shells. The contact type needed direct contact before detonating and needed perfect accuracy. The alternative at the time was a timed fuse, set individually for each fuse and often resulted in the bomb exploding before reaching its target. If the timer was set too long, the fuse could be put out when it has landed. These fuses were especially poor in dealing with aircraft. This was due to the extreme accuracy (and luck) which was needed to hit them.
Fitting a technically superior fuse was an incredibly complex task. British researchers initially sought to develop light-sensitive receptors to determine proximity to a target. Light was an extremely difficult measure to work with, and was hampered by reflecting light. These were also unusuable at night. The first device was designed in Britain using a breadboard circuit. After some initial issues involving withstanding the necessary force – British research was shared with the United States in September 1940. This would lead to the first development of the working fuze, using a breadboard.
American Development and Use
The previously mentioned experiments were then improved by american researchers and tested successfully for the first time. There were initial issues with components withstanding high force levels without breaking. The answer was in mounting the tubes necessary for the function of the fuse in plastic and coating them in wax. After this success, the fuzes started to be tested specifically for use as anti-aircraft artillery. One of these tests occurred using drone aircraft targets over Chesapeake Bay in August 1942. Every single drone used in the test was destroyed – making this test an extreme success. This would lay the foundations of the practical use of the proximity fuze in World War II. Using the fuze amongst a newly invented automatic tracking radar and fire control computer allowed many flying bombs to be shot down across London and Antwerp. These were extremely hard to shoot down due to their speed, but were far more easily stopped thanks to the invention.
How Did The Final Proximity Fuze Work?
In short, the fuze essentially sensed radar returns from the ground. The explosive charge while the shell was still 20 to 50 feet in the air. It did his using transmitters and receivers using various tubes. As the target got closer, the oscillator’s energy would be reflected back to the fuze. The strength of this signal depended on the distance to the target. When the signal reaches a certain level, the 4th tube is targeted and the detonator is set off.
Proximity Fuze’s Role In The War
Vannevar Bush, head of the U.S Office of Scientific Research and development directly credited the proximity fuze with three roles.
- Stopping German V-1 bomb attacks directed towards England as a key part of anti-aircraft batteries
- Greatly improved defense efforts against Japanese kamikaze attacks in the Pacific
- Revolutionised land warfare when used against German infantry in Europe
The fuze was extremely successful in establishing PCBs as an essential to devices. It set a standard for the effectiveness of PCBs in creating new, innovative products and devices despite not being too well known worldwide due to the nature of it’s secretive creation and use in the war.