The video shows a circuit of a Astabile Multivibrator that drives a 12 Volt – 8 A motor via a Darlington. That Darlington drives a relay every 6 seconds in a reversed way (other 6 seconds: non reversed). The time (2 directions) is set with the help of 2 potentiometers & electrolytic capacitors.
It is a simple (say: primitive) analog circuit that can help with pump circuits etc; as long as the timing is not critical.
Deviations say 5-10 %. For real critical timing you need a clock oscillator.
That is not used here, the time is set by the R-C combination.
Electrolytic capacitors, used as timing elements, (can) act different due to aging, temperature, etc. And their tolerance is often 10 or more %. Idea: use the best ectrolytics that you can buy when you want to use this circuit. And: higher voltage electrolytics have better properties (related to timing) compared to low voltage electrolytic capacitors.
Important: the sparking on the contacts of the relay (though damped with the capacitors) can give the relay a limited lifetime. Read: only the relay, the transistors will more or less work “forever”. Of course the electrolytics wil age; after (say) 10 years they must be replaced.
Use in this circuit good quality electrolytic capacitors say from Philips or Matsushita or Sony or Samsung.
Remarks:
1) On 0.33 I say that it is a 12 V motor but it is a 24 V motor. Does not have an effect on the circuit;
2) On 4.49 I say that the end-transistor in the Darlington driving the relay burned out constantly. This only happened with other circuits (TL 071 & more & other circuit in the video), no burning out or problems were seen with the circuit published in this video;
3) On 6.06: the sparks are not visible, sorry for that. I left the lamps in my living room “on” because of more light in this video. When you make this circuit you will see small (damped) sparks when you look at the relay contacts in complete darkness. Of course relay contacts can handle some (small) sparks, but it is better to avoid them (longer lifetime of the relay).
Simple things: a resistor and/or with a parallel capacitor (as long as the switch circuit can handle that ….. over the relay contacts)
4) On 7.22: this only shows the spark-damping capacitors, not the complete circuit, so go to 5.23 for more info (how to connect the motor);
5) On 9.50: the published circuit works overall properly.
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There are (some) links to my video’s on YT available on my Channel Trailer in the “comments” section. Select, in the comments section, always “NEWEST FIRST” to get the right overview.
My books about electronics & analog radio technology are available via the website from “LULU”, search for author “Ko Tilman” there.
Some of my books (not all) are available via Barnes and Noble and via Amazon.
But all my books (the complete bunch) are/is available on the website of LULU.
Regarding all my video’s: I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics with real properties for a purpose) and important adaptations to the circuits.
Be aware of that, I saw on the internet my circuits reproduced in a poor or not proper way.
I also found that people probably republish my circuits under phantasy names and/or with phantasy properties, attributing electronic properties to them that they were never made for, so phantasy properties. Sometimes they want to find gold with them. I take distance from all these fake claims; I cannot help that it happens, sorry. Upload 5 April 2020.
Important: I made 3 experimental electronic circuits to reach this goal, only this circuit (!) worked properly and was durable, could handle overload & problems and (in my opinion) can work for years. Only the relay durability is a factor, but there are very durable relays that can switch during many years (the high quality ones, with (say) expensive contact materials). Video NOT made for children.
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