This page describes a personal computer system which has been modified to make it more tolerable by reducing the electromagnetic emissions. The system employs:
- shielding for the computer, keyboard, trackball, LCD monitor and its power supply.
- a modified LCD monitor equipped with an LED backlight
- the LCD monitor is powered by a linear power supply using matched toroid transformers.
- a passive filter blocks the monitor noise from emitting onto the power line.
- all of which are placed at a distance from the user.
A tutorial describes in detail how the LCD monitor was modified
*Tutorial LCD/LED Monitor*
This system is being developed and tuned by an electrical/biomedical
engineer who suffers from Electrosensitivity. Improvements in lower EMF emissions are litterally felt. His quest is to be able to comfortably use a computer again. For him, the average computer or laptop is intolerable after just several minutes of use (symptoms include an unbearable heaviness of being (almost like a slow motion electrocution), clinching chest pains, tremors (especially in the forearms), wailing tinnitus) and a headache. Whereas this computer can be used for several hours with considerably less symptoms.
Computer
A laptop PC, equipped with an ulta-low voltage processor, is placed twenty feet away from the user. It is heavily shielded inside a heavy duty mu metal case.
LCD Monitor
The laptop drives an external LCD monitor which is a 17" retrofitted with an LED backlight. The switching power supply circuit board has been removed from the chassis and replaced with a custom linear power supply, also remoted 20 ft. Another custom, linear current regulated power supply drives the LEDs. Components within the LCD monitior itself are shielded with mu metal.
Keyboard/Trackball
The USB keyboard and tackball are shielded internally and externally with mu metal, decreasing EMF exposure. Direct from the factory, the keyboard and trackball caused severe tinnitus, which the shielding improved.. Here is a pic of the mu metal that was placed inside the keyboard. It was a tedious job drilling all of the holes. There is also a sheet of mu metal on the bottom of the keyboard. Keyboard Shield
Measurements
Instruments used to measure the EMF include
- a Trifield 100XE meter (to measure magnetic fields),
- an Alpha Labs 'RF Field strength Meter' (to measure High Frequency Radio Frequency (RF) pollution),
- and a Grundig Mini 300 world band receiver (to measure the tone of the emitted lower frequency RF).
The meters can be obtained on-line from stores such as LessEmf. For anyone suffering from Electosensitivity such meters are essential to track down offensive sources of electromagnetic pollution.
Three computers are compared with respect to their EMF emissions. Listed are the measurements of EMF emitted from the various components (mouse, keyboard, monitor, etc.). The first computer is the low emission computer described here composed of an HP 2510p ultra portable laptop with a customized 17" LCD monitor, the second is a Dell Dimension E520 (Core 2 6320 1.86 GHz, 2 Gig RAM) with a 17" DCLCD LCD monitor, the third a Dell XPS 410 (Core 2 6320 1.86 GHz, 2 Gig RAM, NVIDA GeForce Graphics card, sound blaster card) with an 20" Dell Ultrasharp monitor (2007WFP)
RF measurements were taken with the meter standing free, rather being held in hand. The front of the meter is held directly abut to the object being measured. The 'zero' adjust option of the RF meter was used to set the measured ambient value was zero.
For magnetic field measurements the front of the Trifield meter is also held directly against the device being measured with the meter held in the hand. Same goes for the AM radio.
There's no detectable change in the ambient RF or magnetic field in the room, which stays constant at 0.001 uw/cm2, and 0.2 mili gauss, respectively, whether the computer is on or off. The ambient values vary slightly from day to day, especially the RF readings. These were taken in the morning where less HAM radios are operated in the nothern hemisphere.
Results for Low Emission Laptop (running on its battery)
RF (uw/cm2)
mouse: Top 0.006
Keyboard: Top 0.003 Bottom 0.007
Video cable: 0.001
Monitor Power Cable: 0.001
Monitor: 0.006
Computer: 0.001
Monitor Power Supply: 0.004
Magnetic Field (milli Gauss):
mouse: Top 0.2, Bottom 0.2
Keyboard: Top 0.2, Bottom 0.2
Video cable: 0.2
Monitor Power cable: 0.2
Monitor: Front 0.2, Back 0.2
Computer: 0.6 max, AC Power Adapter (when used) 0.5
Monitor Power Supply: 4.0
Microwave Band Sound:
mouse: nearly silent fuzz
Keyboard: Mild Tone
Monitor Low Frequency Fuzz fairly strong especially in upper front.
Results for Dell Dimension 520
RF (uw/cm2)
mouse: Top 0.013
Keyboard: Top 0.006, Bottom 0.049
Monitor cable: 0.016
Monitor: 0.059
Computer: 0.016
Magnetic Field (milli gauss):
mouse: Top 0.4, Bottom 1.4
Keyboard: Top 0.2, Bottom 0.2
Monitor cable: 0.5
Monitor: Front 1.5, Back 15
Commputer: Front 3.0, Rear (by Power supply) 50.0
Microwave Band Sound:
mouse: Mild Fuzz
Keyboard: High Pitch Tone, Fuzz
Monitor High Pitch Tone, Fuzz
Results for Dell XPS 410
RF (uw/cm2)
mouse: Top 0.010
Keyboard: Top 0.008, Bottom 0.015
Monitor cable: 0.002
Monitor: 0.014
Computer: 0.009
Magnetic Field (milli gauss):
mouse: Top 1.0, Bottom 1.5
Keyboard: Top 0.6, Bottom 1.8
Monitor cable: 0.8
Monitor: Front 37.0, Back 10.0
Computer: Front 15.0, Rear (by Power supply) 100.0
Microwave Band Sound:
mouse: Mid Pitch Tone, Fuzz
Keyboard: High Pitch Tone, Fuzz
Monitor: Various High Pitch Tones, Fuzz
Discussion
Developing low emission equipment is an art that requires laborious hours of trial and error. It's as mysterious an occupation as electrosensitivity is an intriguing disease.
Consider that the ambient fields measured at the body of the user, using the meters at hand, are nearly indistinguishable whether the computer is on or off. Yet the affects are clearly noticed by the electrosensitive person. This suggests that the fields travel far further than one would expect, and that the electrosensitive person is extremely sensitive.
The most obvious difference in the RF measurements are seen in the monitor, 0.006 (LED Baclight) vs. 0.059 (DCLCD), nearly a thirty fold increase. Also note the bottom of the keyboards, 0.007 vs. 0.049. These results suggest that one should avoid laying a keyboard on the lap.
It's unclear why the XPS monitor and keyboard have relatively low measured RF fields. However, when one analyzes the sound broadcasted from the radio one sees that the mouse, keyboard, and monitor emit distinct tones, whereas the low emission components have at most muted tones, and mostly fuzz. One may deduce that the mu metal shielding is affective in muting these tones, and/or spreading them out across a braoder frequency range. For an electrosensitive person suffering from tinnitus , these distinct tones are particularly annoying in that those tones are replicated, somehow, in the ears.
As for magnetic fields, the Dell XPS computer emits a staggering 100 mili gauss towards the rear, whereas the low emission computer emits at most 1.0 mili gauss. The Dell E520 is in the middle at 50. Also notice the magnetic field emitted by the Dell XPS monitor (2007WFP) at 37 milli gauss in the front, whereas the low emmission Samsung is a mild 0.2. The DCLLCD monitor also emits a mild 1.5 at the front. This monitor was hand picked for it's relatively low emissions, as the Dell E207WFP that came with the E520 computer wss returned because it caused severe tinnitus and discomfort. The XPS monitor (2007WFP) was retained by the owner because he is not electrosensitive. Therefore, do not conclude that the 2007WFP model is more tolerable than the E207WFP. Neither is acceptable for an electrosensitive person.
The conventional mouse also emits significantly more magnetic field, measured at 1.0 on the top and 1.5 mili gauss 4 on the bottom. Whereas the shielded trackball is at a low 0.2.
LCD Monitor is an Enemy
An LCD monitor is most likely the worst offender to the electrosensitive. It has long been known that it contributes to severe tinnitus and other ill feelings.
The first experiment involved replacing the cold cathode tube lamps with LEDs. This offered very little relief.
The next obvious offender was the power supply. After that was remoted, the symptoms were significantly better. Also note that the LEDs were chosen because they are efficient, produce a pure white light, and run on low a voltage. It would have been nearly impossible to run the 750 volts supplied to the cold cathose bulbs over 20 feet!
However, even with the remoted LCD power supply, a low frequency form of tinnitus still persisted. This was alleviated by shielding the main LCD circuit board inside the monitor with a sheet of mu metal.
The last improvement was the addition of a low pass filter on the power line feeding the main board of the LCD monitor. The filter, placed near the main board, substantially reduced the higher frequencies from traveling back onto the power cable, thus lowering the measured magnetic field on that cable, and noticeably made the computer more tolerable. The LCD monitor is shrouded with two layers of Veilshield, a fine wire mesh which reduces high frequency RF noise. This is where the monitor stands at this point, despite the Radio Frequency noise (measured with the AM radio) which is still being emitted, especially from the front of the monitor.
Video and Monitor Power Cables
The measured fields emitted by the video and monitor power cables are moderate. Noise from the power cable was mitigated with the filter, thus the video cable is the more troublesome.
A higher magnetic field and RF are emitted by the cables and monitor when the laptop runs from the AC power adapter as opposed to the battery. Thus it may be concluded that noise is transmitted from the computer to the video cable, or is a result of dirty power. Also note that some noise is also transmitted back from the monitor to the power cable.
The video signals can be transmitted over a fiber optic cable, however the high costs of off-the-shelf equipment makes such a solution prohibitively expensive at this time.
Linear vs. Switching Power Supplies
The power supply originally equipped with the monitor produces very dirty power. What are suppose to be DC power signals, are spoiled with sinister spikes, or impulses, of noise at about 30 kHz.
The strategy was to build both custom switching and linerar power supplies for the monitor and LEDs, then choose the one with the best results.
Linear supplies have the advantage of providing relatively clean power compared to switching supplies. Linear supplies eliminate the impulses at 30k Hz. The downside to linear supplies is the magnetic field at the transformer, which can be minimized by matching the transformer size to the load, and double windings. The magnetic field at the power supply is 4.0 milli gauss (with heavy shielding) which is reduced to 0.2 at a distance of 1 ft. A big advantage to the switching supplies is the very low magnetic field, 0.2 milli gauss shielded. Overall, the comfort level is greater with custom linear power supplies when compared to switching supplies.
Low pass filters ineffectively clean up the high frequency noise produced by the switching supplies before the DC power enters the monitor and LEDs. A 60 Hz component is prominent in the LCD power supply, though no such noise is in the power to the LEDs. It is therefore concluded that the 60 Hz noise is generated by the LCD monitor. 60 Hz noise is also prevalent in the power supplied to the laptop computer, so the noise is not singular to the LCDs. A passive low pass filter place between the monitor and power supply sufficiently cleans the 60 Hz noise. The magnetic field on the LCD power line is negligible.
Here is a snapshot of the LCD power (switching supply - AC component only) without any filtering, LCD Power No Filter The overall noise has an amplitude of over 100 millivolts (peak to peak) out of a 5 volt DC power supply. The "halo" or hazy ghost about the noise are the infamous impulses, intrinsic to switching power supplies, which occur every 30k Hz. Next is a shot of the LCD switching power with filtering, LCD Power Filtered The Total amplitude has been reduced to 40 milli volts, and the high frequency noise has been significantly reduced from 40 milli volts down to 10. Here is a pic of the LED power (switching suppy - filtered), LED Power Filtered. There is no 60 Hz noise seen in the LED power. The prevalent high frequency, switching mode noise has an amplitude of 10 milli volts, up to 35 including the "halo" of 30k Hz impulses.
The power produced by the linear supplies is considerably cleaner and better regulated. The 60 Hz noise generated by the monitor is quenched with a passive LC filter, the amplitude which is less than 20 milli volts. This sinister looking waveform is the unfiltered noise emitted by the main board of an LCD monitor. LCD Power The waves are broadcasted as electromagnetic waves. But you don't have to show an electrosensitive person the broad spectrum of the composite wave, and how the 60 Hz wave fiercely dips to a vertical 'V'. Rather, he can feel it. Non-sensistive people may not feel these waves, but they are imputing deleterious biological affects. The mid-band 30k Hz noise, seen as a halo, can cause a myriad of acute affects to electrosensitives. There is also an entire spectrum of higher frequencies not visualized by an oscilloscope.
Much worse are the emissions from a mini projector. Here is a pic of the noise emitted by a Mitsubishi Pocket LED Projector, again using a clean linear power supply: Projector Power Viscious spikes over three volts in amplitude explains why this projector causes severe discomfort to use, and therefore is not an alternative to the LCD monitor. Heavy shielding is hopelessly inadequate for such a bothersome device.
Shielding
Shielding can result in a fiasco, or in other cases may help. For instance, the shielding on the main board of the LCD monitor was essential to relieve some of the tinnitus. Yet attempts thus far in shielding the entire LCD monitor resulted in a drastic increase in tinnitus. Also shielding the LCD power cable in flexible steel conduit was terribly uncomfortable.
An attenpt to shield a mini LED projector was the biggest disaster of all. Endless days spent on fabricating a double layered mu metal shield put me on my back after testing it for eight hours. The tremors were terrible for weeks. The magnetic field and mid-band frequencies were impressively reduced, yet the RF was still significant at the case. It therefore may be deduced that high RF pollution is a major contributor to the ill symptoms. A similar situation exists with the trackball. The mu metal shield reduces the magnetic field, superlatively reduces mid-band noise picked up by an AM radio, but the emitted RF is actually increased.
Here are a few pics of the mu metal case for the projector. It employs 2 layers of 50 mil mu metal. Projector Case Projector Case w/ Fans Projector Case Inside View Projector Case Aperture
Some purport that at least a 6 inch distance between the RF source and the shield is required, otherwise the shield behaves as a radiator. In fact, the inner shield is close to the projector and does induce mid-band frequencies.
Wireless Networks
The worlds love affair with WiFi (and wireless devices in general) is criminal. Not only are people harming themselves, but they're infringing on the well being of electrosensitives. Use wired Ethernet. If one must use wireless, a suggestion is to shield the antenna of the wireless router, as shown. Such a simple mu metal shield significantly reduces the RF emitted by the router, yet the wireless still works. Wireless Shield
Conclusion
This project has shown a way to reduce the emf emissions from a computer to make it more tolerable for those with certain sensitivities. The computer still emits offensive EMF, and therefore can be used for a limited time per day. It is still far better than the average computer.
The task of building a practical computer that is completely tolerable for the emf sensitive is nearly an impossible feat. Such a system must be designed from the ground up, suppressing the bothersome spectrum of frequencies emitted by the various components. The system described here just scratches the surface of solving this insurmountable problem.
Three computers were compared with respect to their EMF emissions. The evaluation has indicated that the emitted magnetic field fairly indicates the degree of subjective electrosensitive symptoms.
Contact
Send inquiries to eli@ahappyhabitat.com
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