Charger with timer for nickel-cadmium batteries. Scheme, description

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Charger with timer for nickel-cadmium batteries. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

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The mains voltage of 230 V is supplied to the primary winding of the transformer T1, and through its secondary winding, rectifier diodes D1 and D2 on the smoothing capacitor C2, the supply voltage of the circuit is obtained.

(click to enlarge)

The time delay unit (timer) is powered through diode D3, resistor R1 and zener diode D4, which provides a safe voltage level for the CMOS chips used. These CMOS chips (IC1 and IC2) draw so little current that the timer block continues to run for 30 seconds after a power outage, preventing the timer block from restarting on short dips or interruptions in the AC line.

The 1V type IC4060 is a 14-bit frequency divider with a built-in oscillator. When the switch S1 is pressed, all its outputs are set to the state of the log. 0, so diode D5 is closed and the built-in oscillator is running. With the indicated values of the elements, its frequency will be approximately 0,17 Hz, so that the last output of the divider (pin 3) will switch to the log state. 1 after about 14 hours. In this case, the diode D5 opens and stops the generator. The first timer from the 2 type IC7556 CMOS chip is connected according to the pulse generator circuit with a frequency of about 0,5 Hz and a duty cycle of about 1:5. Pin 4 is the timer reset input, active low - when the corresponding signal is received from the output of IC1, the timer output goes to log.0.

The second timer is used simply as a powerful inverter, and a high level at its output through resistor R8 turns on a stable current generator on transistors TR3 and TR1. When IC1 counts to the end, the oscillator on IC2 begins to work, and the stable current generator starts to generate current pulses with a duration of 400 ms every 2 s. Nickel-cadmium cells have a fairly high self-discharge rate: about 10% capacity per week. If left in the charger, they are kept fully charged and always ready to use. In this case, overcharging is excluded, and the transition to the current pulse mode is accompanied by the blinking of the D10 LED, which means the completion of the main charge and the readiness of the battery.

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Neurons with ears 27.09.2015

Neuroscientists often use optogenetic methods, where neurons in the brain of a test mouse are activated by light. The neuron is supplied with a photosensitive membrane protein, which, under the action of light, opens ion channels in the membrane; the redistribution of ions between the inner and outer sides of the membrane generates a nerve impulse. Light can be "conducted" into the brain with the help of a fiber optic light guide, as far as the gene for a photosensitive protein, then genetic engineering tricks come to the rescue. Optogenetics allows you to selectively control clearly defined groups of neurons, which, of course, gives us a lot of information about the work of individual nerve circuits and entire regions of the brain.

But light is not the only switch that can be used here. Researchers at Salk University have created an alternative sonogenetic method, named after the optogenetic one. By the name, you can understand that here we are talking about sound, or rather, about ultrasound, which triggers a neural impulse. Ultrasound causes mechanical vibrations, that is, neurons need an ion channel that opens and closes in response to a mechanical stimulus. Stuart Ibsen and his colleagues used TRP-4 as such a channel, activating its gene in various nerve cells of the roundworm, the nematode Caenorhabditis elegans.

In order for the ultrasonic signal to work, it was transmitted not through air, but through water, in which dishes with worms were immersed. For additional enhancement, a lipid solution was also added: after removing the solvent, the lipids formed a layer of microbubbles, which served as additional resonators. With the help of short sound impulses, it was possible to make freely crawling worms change the direction of movement or regulate the frequency of contractions of the body. The specific effect depended on which neurons were equipped with "ears" - the mechanosensitive membrane protein TRP-4. By itself, it belongs to the genome of the nematode, so if you try to do the same in mice or rats, you will first have to find out how TRP-4 will behave in a completely unrelated organism. However, according to the authors of the work, for these purposes, one can try to change the protein itself, increasing its efficiency and compatibility with foreign cells, or else find some other natural analogues. The experimental results are published in Nature Communications.

The advantage of sonogenetics is that there is no need to introduce a sound guide into the body - ultrasonic vibrations come to neurons from outside. (However, it is worth noting that options have appeared in optogenetics when researchers are limited to external light irradiation with increased permeability, and light-sensitive proteins in neurons respond to a signal reaching them through the thickness of tissues.) In addition, the authors of the new method propose the use of multichannel sound so that different neurons "hear" something of their own, and as a result, it would be possible to immediately observe the work of several nerve circuits.

Previously, there have already appeared works devoted to the stimulating effect of ultrasound on the brain of animals and humans; and Sony even patented a technique that would allow gamers to smell, taste and hear sounds, all thanks to sound stimulation. In the case of sonogenetics, we are talking about the most specific effect, focused on individual nerve cells, however, due to the necessary genetic engineering manipulations, this method is unlikely to ever be used on humans.

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