MineCam
Encyclopedia
The MineCam is a remote exploration camera built by I.A.Recordings
. It is used for mine shafts exploration and other similar environments. It was originally conceptualized in 1988, and since went under several design revisions. The name MineCam, is a pun on MiniCam, an early hand-held broadcast camera built by CBS Laboratories
.
first had the idea for what became "MineCam" in 1988. He had been visiting some metal mines in Wales
with the Shropshire
Caving and Mining Club and spent several hours setting up a single rope technique
rig to descend a remote shaft, only to find that there were no ways off at the bottom. This was the motivation to build a miniature camera which would allow enthusiasts to explore hard to reach, unsafe, or impossible to reach areas.
The remote exploration of mines prior to 1988 had been done commercially for several years by pipeline camera firms
using equipment that needed to be housed in a vehicle and powered by a generator. Many old mine shafts are remote from roads though, so Peter's final goal was a small lightweight battery-powered kit which could be carried on foot. The first two versions of MineCam did not achieve this, but tested various approaches with the video technology available at the time.
MineCam 1 worked, but the monochrome image was sometimes difficult to interpret. It was time to try colour, and this was not yet available from the commercial shaft inspection firms.
chip was removed and put in a round tobacco tin connected by a short cable to the rest of the electronics in a small Eddystone die-cast box. The 'Eddy box' contained extra hardware to convert the Y/C (700 kHz) direct colour-under
output to composite PAL
, and provide various unusual power supply voltages. Because of the colour stripe filter and the early technology, this CCD was only as sensitive as the monochrome vidicon.
Both MineCam 1 and 2 needed to be lowered twice to investigate a shaft. First, they were lowered looking vertically down, and notes made of the depth and heading of any interesting features. The camera was then hauled to the surface and re-rigged to look horizontally at the interesting items found earlier. A remote tilt mechanism was needed as it would halve the time and effort.
To indicate heading, MineCams 1 and 2 used an ordinary spherical fluid-mounted car compass on an aluminium arm about 30 cm from the camera. A supplementary lens (from an old pair of spectacles) glued to the acrylic window brought the compass into focus at the corner of the frame.
. It was also much more sensitive, so the light could be smaller and a remote tilt mechanism became practicable. A coded control signal was needed that would go down the video cable to save using extra wires, so a model radio control system was adapted, giving 2 proportional channels for tilt and eventual pan movements. The 27 MHz carrier was easily combined and split from the baseband video. The first tilt motor was a standard model control servo with 180 degree rotation. The camera head and light were mounted in an open-framework cage about 25 cm long, rotated on a horizontal axis by the servo. Despite taking care, motor gears were frequently stripped when the cage hit obstacles and the servo had to be replaced regularly! The light source needed to pan with the camera, so had to be small enough to fit in the cage. A 12 V 50 W quartz-halogen lamp with 5 cm diameter integral dichroic reflector was fitted, powered from a small switch-mode PSU. Although the lighting power had been reduced, it still required a high voltage supply down the cable to reduce voltage drop, so 240 V was still used.
The cage rotated in an aluminium yoke attached to the bottom of a waterproof plastic box containing the rest of the electronics, including a power supply for the camera.
To be able to use the system in locations remote from mains power and not accessible by a vehicle carrying a generator, I.A.Recordings obtained a 150 W inverter
and 12V lead-acid battery from an outdoor leisure shop.
MineCam 3 was the first to use an electronic compass for heading display. Tandy (Radio Shack) had developed a device using a flux gate sensor to give x & y components of the Earth's magnetic field which drove the orthogonal windings of a 360 degree mechanical indicator, for use as a car compass. I.A.Recordings discarded the indicator and used the x & y voltages to control the position of a flashing spot added to the video picture. This gave a compass-circle type display on screen. If the x (east-west) signal was inverted, when looking vertically down, the spot appeared to be fixed above a point on the ground as the camera rotated.
Electromagnetic interference from the switch mode power supply and harmonics of its square-wave power waveform appeared in the video signal as noise. This was reduced by careful layout , screening and the use of a single-point ground return.
The miniature camera was waterproofed by sliding it into a square-section 25 mm wide aluminium tube (only slightly bigger than the camera), with a glass window glued in one end, and a cable gland at the other. The waterproof container sold for this camera was too large and heavy for the MineCam, but the aluminium tube is not as watertight. It has an IP rating of between 66 and 67.
geared dc servo motor was used, driven from the remote control receiver, and a thrust bearing and Oldham coupler. The motor's powerful magnet interfered with the compass sensor so a sheet of mu-metal
donated by a helpful local firm was formed into a screen round the whole motor & gearbox assembly. The tilt servo did not seem to cause the same problem, as it is smaller and rotates with the sensor on the yoke. Wherever possible, all hardware is plastic or non-ferrous metal.
Other improvements in MineCam 4 include a high-torque tilt servo, a microphone with balanced amplifier, a laser diode module beside the camera to produce a spot of light on the subject for range and size estimation and experimentation with bat detection and gas sensors.
The control box is and contains a power supply, the servo control transmitter and a video equaliser. The cable is now 200 m of thin multi-core containing one coaxial and 5 single wires. As it is not load-bearing, a rope still has to be used and 9 mm static climbing rope was found to be better than anything thinner, including wire rope, at preventing twist. The rope often becomes tangled with the cable, so I.A.Recordings is still looking for a weight-bearing cable. The 180 degree tilt range allows the underside of shaft caps to be inspected. Compared with commercial versions which were still monochrome and used a mirror to switch the image from vertical to horizontal, the MineCam was much more flexible, and the goal of having a complete system that could be carried by individuals on foot had been reached. The picture was recorded on U-Matic
, then Hi-8 and now on mini-DV tape.
" or "Blondin
" arrangement. A large diameter pulley (a Sinclair C5
wheel) is mounted on a trolley which is winched along a wire rope slung across the shaft and kept in tension. When the pulley is centred, the traverse rope is locked-off and the camera lowering rope can be released.
The 50 W lamp & reflector is a convenient size and is available in a variety of beam-widths, but the idea of the dichroic reflector preventing heat being reflected forward is actually a disadvantage for the MineCam. The lamp head has to be enclosed to protect it and to screen the power supply interference, but without careful internal design of reflectors and baffles, the housing can get very hot.
MineCam 4 has proved reliable and useful and gives a high-quality colour picture good enough to use in video productions. It is featured for example in the I.A.Recordings video "Snailbeach".
I.A.Recordings
I.A.Recordings was founded in 1982 by a small group of volunteers, to record past and present industries on film and video, as a resource for industrial archaeology ....
. It is used for mine shafts exploration and other similar environments. It was originally conceptualized in 1988, and since went under several design revisions. The name MineCam, is a pun on MiniCam, an early hand-held broadcast camera built by CBS Laboratories
CBS Laboratories
CBS Laboratories or CBS Labs was the technology research and development organization of CBS...
.
History
Peter Eggleston of I.A.RecordingsI.A.Recordings
I.A.Recordings was founded in 1982 by a small group of volunteers, to record past and present industries on film and video, as a resource for industrial archaeology ....
first had the idea for what became "MineCam" in 1988. He had been visiting some metal mines in Wales
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
with the Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...
Caving and Mining Club and spent several hours setting up a single rope technique
Single Rope Technique
Single Rope Technique is a set of methods used to descend and ascend on the same single rope. SRT is used in caving, potholing, rock climbing, canyoning, roped access for building maintenance and by arborists for tree climbing.-Historical Developments:...
rig to descend a remote shaft, only to find that there were no ways off at the bottom. This was the motivation to build a miniature camera which would allow enthusiasts to explore hard to reach, unsafe, or impossible to reach areas.
The remote exploration of mines prior to 1988 had been done commercially for several years by pipeline camera firms
Pipeline video inspection
Pipeline video inspection is a form of telepresence used to visually inspect the interiors of pipelines. A common application is to determine the condition of small diameter sewer lines and household connection pipes....
using equipment that needed to be housed in a vehicle and powered by a generator. Many old mine shafts are remote from roads though, so Peter's final goal was a small lightweight battery-powered kit which could be carried on foot. The first two versions of MineCam did not achieve this, but tested various approaches with the video technology available at the time.
MineCam 1
MineCam 1 used a monochrome vidicon camera in a waterproof housing made out of a 10 cm plastic sewer pipe and fittings, with an acrylic window. This was successfully tested in the deep end of a swimming pool. The camera was insensitive - it needed a 150 W lamp, which required a 240 V supply, but so did the camera. The cable was 100 m of video co-axial and power, taped together at 2 m intervals and numbered to give a crude depth measurement. The camera and lamp were heavy, so an old 6 mm static climbing rope was used to support it. The monitor was a 10 cm portable TV.MineCam 1 worked, but the monochrome image was sometimes difficult to interpret. It was time to try colour, and this was not yet available from the commercial shaft inspection firms.
MineCam 2
MineCam 2 used parts from a disused Sony 'Handycam.' The colour CCDCharge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
chip was removed and put in a round tobacco tin connected by a short cable to the rest of the electronics in a small Eddystone die-cast box. The 'Eddy box' contained extra hardware to convert the Y/C (700 kHz) direct colour-under
Heterodyne
Heterodyning is a radio signal processing technique invented in 1901 by Canadian inventor-engineer Reginald Fessenden where high frequency signals are converted to lower frequencies by combining two frequencies. Heterodyning is useful for frequency shifting information of interest into a useful...
output to composite PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
, and provide various unusual power supply voltages. Because of the colour stripe filter and the early technology, this CCD was only as sensitive as the monochrome vidicon.
Both MineCam 1 and 2 needed to be lowered twice to investigate a shaft. First, they were lowered looking vertically down, and notes made of the depth and heading of any interesting features. The camera was then hauled to the surface and re-rigged to look horizontally at the interesting items found earlier. A remote tilt mechanism was needed as it would halve the time and effort.
To indicate heading, MineCams 1 and 2 used an ordinary spherical fluid-mounted car compass on an aluminium arm about 30 cm from the camera. A supplementary lens (from an old pair of spectacles) glued to the acrylic window brought the compass into focus at the corner of the frame.
MineCam 3
Mark 3 was radically different. A high quality colour camera became available, a Pulnix TMC-X not much bigger than a Mini-MagliteMaglite
Maglite is a brand of flashlight manufactured in the United States by Mag Instrument, Inc. located in Ontario, California, and founded by Anthony Maglica. It was introduced in 1979. Constructed principally of anodized 6061 aluminum, they have a variable-focus beam...
. It was also much more sensitive, so the light could be smaller and a remote tilt mechanism became practicable. A coded control signal was needed that would go down the video cable to save using extra wires, so a model radio control system was adapted, giving 2 proportional channels for tilt and eventual pan movements. The 27 MHz carrier was easily combined and split from the baseband video. The first tilt motor was a standard model control servo with 180 degree rotation. The camera head and light were mounted in an open-framework cage about 25 cm long, rotated on a horizontal axis by the servo. Despite taking care, motor gears were frequently stripped when the cage hit obstacles and the servo had to be replaced regularly! The light source needed to pan with the camera, so had to be small enough to fit in the cage. A 12 V 50 W quartz-halogen lamp with 5 cm diameter integral dichroic reflector was fitted, powered from a small switch-mode PSU. Although the lighting power had been reduced, it still required a high voltage supply down the cable to reduce voltage drop, so 240 V was still used.
The cage rotated in an aluminium yoke attached to the bottom of a waterproof plastic box containing the rest of the electronics, including a power supply for the camera.
To be able to use the system in locations remote from mains power and not accessible by a vehicle carrying a generator, I.A.Recordings obtained a 150 W inverter
Inverter (electrical)
An inverter is an electrical device that converts direct current to alternating current ; the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits....
and 12V lead-acid battery from an outdoor leisure shop.
MineCam 3 was the first to use an electronic compass for heading display. Tandy (Radio Shack) had developed a device using a flux gate sensor to give x & y components of the Earth's magnetic field which drove the orthogonal windings of a 360 degree mechanical indicator, for use as a car compass. I.A.Recordings discarded the indicator and used the x & y voltages to control the position of a flashing spot added to the video picture. This gave a compass-circle type display on screen. If the x (east-west) signal was inverted, when looking vertically down, the spot appeared to be fixed above a point on the ground as the camera rotated.
Electromagnetic interference from the switch mode power supply and harmonics of its square-wave power waveform appeared in the video signal as noise. This was reduced by careful layout , screening and the use of a single-point ground return.
The miniature camera was waterproofed by sliding it into a square-section 25 mm wide aluminium tube (only slightly bigger than the camera), with a glass window glued in one end, and a cable gland at the other. The waterproof container sold for this camera was too large and heavy for the MineCam, but the aluminium tube is not as watertight. It has an IP rating of between 66 and 67.
MineCam 4
For MineCam 4, the final major development was a pan motor. It was difficult to arrange a system which allowed 360 degree rotation of the tilt yoke whilst maintaining connections for video, tilt servo, lighting power, camera power and flux-gate sensor. An RS ComponentsRS Components
RS Components, commonly known as RS, is a global, world leading industrial component distributor headquartered in Corby in the United Kingdom. It distributes to the United Kingdom, most of Europe and Asia and is part of the Electrocomponents group....
geared dc servo motor was used, driven from the remote control receiver, and a thrust bearing and Oldham coupler. The motor's powerful magnet interfered with the compass sensor so a sheet of mu-metal
Mu-metal
Mu-metal is a nickel-iron alloy that is notable for its high magnetic permeability. The high permeability makes mu-metal very effective at screening static or low-frequency magnetic fields, which cannot be attenuated by other methods. The name came from the Greek letter mu which represents...
donated by a helpful local firm was formed into a screen round the whole motor & gearbox assembly. The tilt servo did not seem to cause the same problem, as it is smaller and rotates with the sensor on the yoke. Wherever possible, all hardware is plastic or non-ferrous metal.
Other improvements in MineCam 4 include a high-torque tilt servo, a microphone with balanced amplifier, a laser diode module beside the camera to produce a spot of light on the subject for range and size estimation and experimentation with bat detection and gas sensors.
The control box is and contains a power supply, the servo control transmitter and a video equaliser. The cable is now 200 m of thin multi-core containing one coaxial and 5 single wires. As it is not load-bearing, a rope still has to be used and 9 mm static climbing rope was found to be better than anything thinner, including wire rope, at preventing twist. The rope often becomes tangled with the cable, so I.A.Recordings is still looking for a weight-bearing cable. The 180 degree tilt range allows the underside of shaft caps to be inspected. Compared with commercial versions which were still monochrome and used a mirror to switch the image from vertical to horizontal, the MineCam was much more flexible, and the goal of having a complete system that could be carried by individuals on foot had been reached. The picture was recorded on U-Matic
U-matic
U-matic is an analog recording videocassette format first shown by Sony in prototype in October 1969, and introduced to the market in September 1971. It was among the first video formats to contain the videotape inside a cassette, as opposed to the various Reel-to-Reel or open-reel formats of the...
, then Hi-8 and now on mini-DV tape.
Rigging
To get the camera out over the centre of larger shafts, I.A.Recordings use either a scaffold pole with a pulley on the end, or for shafts that have run-in so the crater on the surface is several metres wide, they have developed a "Tyrolean traverseTyrolean traverse
A Tyrolean traverse is a method of crossing through free space between two high points on a rope without a hanging cart or cart equivalent. This is used in a range of mountaineering activities: rock climbing, technical tree climbing, caving and water crossings. A zip-line is in essence a Tyrolean...
" or "Blondin
Blondin (quarry equipment)
Blondins were a type of aerial ropeway employed in open pits in the slate quarries in Wales to transport wagons loads of rock between locations. They were named after the famous tightrope walker Charles Blondin.- History :...
" arrangement. A large diameter pulley (a Sinclair C5
Sinclair C5
The Sinclair Research C5 is a battery electric vehicle invented by Sir Clive Sinclair and launched by Sinclair Research in the United Kingdom on 10 January 1985. The vehicle is a battery-assisted tricycle steered by a handlebar beneath the driver's knees. Powered operation is possible making it...
wheel) is mounted on a trolley which is winched along a wire rope slung across the shaft and kept in tension. When the pulley is centred, the traverse rope is locked-off and the camera lowering rope can be released.
The 50 W lamp & reflector is a convenient size and is available in a variety of beam-widths, but the idea of the dichroic reflector preventing heat being reflected forward is actually a disadvantage for the MineCam. The lamp head has to be enclosed to protect it and to screen the power supply interference, but without careful internal design of reflectors and baffles, the housing can get very hot.
MineCam 4 has proved reliable and useful and gives a high-quality colour picture good enough to use in video productions. It is featured for example in the I.A.Recordings video "Snailbeach".