Neurostimulator. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Neurostimulator. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electronics in medicine

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A sedentary lifestyle, illness, and sometimes just laziness atrophy our muscles. Reduced blood supply to muscles and organs. Biologically active points (acupuncture points) lose their connection with each other, which leads to a disruption in the exchange of energy between them. This is fraught with new diseases and deterioration of well-being. The man is fading away. Laziness must be driven away. And for sick people and for people leading a forced sedentary lifestyle, for example at work, this device is intended. The neurostimulator does not pump muscles, as many mistakenly think after watching advertising, but warms them up, increasing blood flow. Such a device is especially needed for people who are in a hospital bed for a long time after car accidents, with spinal injuries, paralyzed. It is good to use it for patients with various kinds of arthritis with limited mobility.

The neurostimulator has the following output pulse parameters:

Output voltage - 100 V.
The duration of the bursts of impulses is 1-70 s.
The period of bursts of pulses is 1-110 Hz.
The pulse duration is 50-250 µs.

The parameters of the output pulses were taken from the website of the developer of the industrial device bodyshapers.com.
Functionally, the neurostimulator consists of two pulse generators, a pulse duration shaper, a voltage converter, and an output amplifier. The pulse generator, implemented on the DD1 chip, outputs pulses with a period of 1 second to 70 seconds (Fig. 1).

(click to enlarge)

The pulse period is set by resistor R2. The pulses of the first generator start the second generator, implemented on the elements DD2.1, DD2.2. The period of these pulses is set by resistor R6. Thus, the duration of the pulses of the first generator is filled with pulses of the second generator. The pause between bursts of pulses is equal to half the period of the first generator. To regulate the subjective sensation, the output pulses have the same duration, generated by the shaper on the elements DD2.3, DD2.4. The duration of the output pulses from 50 to 250 µs is set by resistor R9. At pin 11 DD2.4 we get pulses of negative polarity. Therefore, the output transistor VT3 is open in the pauses between bursts of pulses, and closed during the passage of pulses. The load resistor R10 limits the output current to 27-30 mA, ensuring human safety.

The voltage converter is assembled according to the standard multivibrator circuit on transistors VT1, VT2 of the pnp structure. Transformer T1 is wound on a ferrite ring 30x15x6 2000NM1. Winding 1 contains 2x43 turns of PEV2-0,5 wire, winding 2 contains 2x14 turns, and winding 3 contains 450 turns. Windings W2, W3 are wound with wire PEV2-0,27 (0,30). First, winding W3 is wound, then in two wires of winding W1, W2 .. The end of one winding W1 and W2 is connected to the beginning of the second, ensuring the phasing of the turns. If, after turning on the converter, there is no voltage at the output of the diode bridge, then it is necessary to swap the conclusions 1-3 or 4-6 of the transformer. Resistor R4 is selected according to the minimum current consumption and the stability of starting the converter when the supply voltage is turned on. The current consumption of the converter without load is 20 mA. The total current consumption of the neurostimulator is 60 mA. The power supply transformer must be designed for more current, since for a short time, when turned on, the converter consumes more current. This is due to the installation of oscillator transients.

A drawing of the printed circuit board is shown in Fig. 2, and the location of the elements on the board is shown in Fig. 3.

Neurostimulator. Circuit board of the neurostimulator

Neurostimulator. Location of parts on the neurostimulator board

It is better to make electrodes round from white tin (nickel plated) with a diameter of 40-50 mm. The edges of the electrodes are rounded with a needle file so that the electrode does not cut into the body. After soldering thin wires, the solder side is filled with sealant. On the arms and legs, it is better to attach the electrodes using a shortened elastic bandage. On the torso, you need to make a special bandage with an elastic band and a fastener with buttons or Velcro. If you go to work, bandages can be put on in advance. The approximate location of the electrodes on the body is the beginning and end of the muscle. Approximate installation of electrodes (from the manufacturer) is given in Fig.4.

Neurostimulator. Location of electrodes by muscle groups

It is better to attach the electrodes to gauze moistened with salted water. If there is no gauze (or there is no such possibility), then it is necessary to take care of good contact of the electrode with the body. Otherwise, a burning sensation will be felt under the electrode. The best feeling under the electrode is bursting. As if a muscle were being squeezed from the inside. The usual feeling is vibrations in time with impulses, warming. The strength of sensation is regulated by resistor R9. Changing the position of the electrodes must be done with the neurostimulator turned off. Do not rush to give the maximum duration of exposure impulses - small doses are more healing. It is better to increase the duration. We do not catch diseases in one day, and they need to be treated for more than one day. Make the first switch-on with the electrodes connected so that you can quickly turn off the device or the electrodes. Short-term short circuit of the electrodes against each other is not dangerous. Before connecting the device to the patient, test its effect on yourself, preferably on your feet.

If you will use the device on others, then it is advisable to set an indication of the passage of bursts of pulses. To do this, it is necessary to put any LED from output 13 DD 2.4 through a resistor of the corresponding rating to the minus power supply. The LED and the quenching resistor are mounted on the housing cover.

Publication: cxem.net

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