A 555 timer is an integrated circuit chip that is commonly used in timers, pulse generators, and oscillation circuits. The 555 can be used as a delay device, trigger, or initiating element in a circuit.

The 555 timer was introduced in 1971 by Signy Tic, and is still widely used in the design of electronic circuits due to its ease of use, low price, and good reliability. Many manufacturers produce 555 chips, including traditional models with BJT and versions by design.

In the 80s, there were basically not many chips in China, and because foreign exchange was precious, some imported chips were also given priority to the cutting-edge military industry, and ordinary state-owned enterprises could not get them, let alone sell them in China.

Duan Yun has used this chip many times in his previous life in the university laboratory, and it is characterized by a simple resistor and capacitor to complete a specific oscillation delay effect, which has a wide range of time, from a few microseconds to several hours.

The 555 chip has a wide range of applications, and is often used as a timer in instrumentation, household appliances, electronic measurement and automatic control.

With this kind of chip, Duan Yun can design more complex electrical equipment, and can greatly improve the "performance" and accuracy of many electrical equipment.

It is precisely because of this that when Duan Yun saw this chip, he was so excited in his heart.

"Brother, how much do you sell for this circuit board?" Duan Yun asked.

"One hundred. The tall man raised his eyebrows and said, "If you don't sell a penny, you won't sell it." ”

"One hundred?" Duan Yun pursed his lips when he heard this, and asked, "Can it be cheaper?"

In Duan Yun's memory, this kind of chip is not expensive, and it will only look like two or three yuan in later generations, considering that this kind of chip is still a high-tech product in this era, the price is estimated to be about one dollar, converted to five or six yuan, this kid directly offered a hundred yuan, obviously the lion opened his mouth.

"How much do you want to buy?"

"Twenty yuan, if you sell it, I'll ask for it. Considering that this chip is rare in China, Duan Yun raised the price again.

"What about dreams? There's a chip on it, do you know what a chip is? A serious high-tech product can cost at least a few hundred dollars abroad!" Gao said loudly.

"Hahaha. Duan Yun laughed when he heard this, and said, "I'll give you another ten yuan, but you have to tell me where you got this board, and if you can do it, you will make a deal." ”

"Not for sale!" said the tall man with an impatient expression.

"Goodbye!" Duan Yun turned his head and left when he heard this.

Although he does want the 555 chip, he will definitely not be wronged, in his opinion, the other party opened a hundred yuan purely to treat this thing as a treasure, it is like never seeing money.

After leaving the stall, Duan Yunyou walked around the alley.

It's really a hodgepodge here, there are all kinds of second-hand electronic components sold, at least most of them are of little use to Duan Yun, but it also gives Duan Yun a preliminary understanding of the folk electronic technology of this year.

After all, amateurism is amateurism, and many people just learn some simple circuit design and basic knowledge from magazines, and make all kinds of strange gadgets, which have little practical value at all.

Perhaps for these people, they are so keen to make and display such gadgets, in fact, they don't expect to sell, or maybe they just want to communicate with other enthusiasts and get some compliments, which is also a nice joie de vivre.

In addition, there are some people who can really make money by relying on technology, Duan Yun saw that some of the customers who came here were looking for masters to repair and modify electrical appliances, and left their names and addresses to facilitate the door-to-door after the negotiation, as for some rich young people came here to buy some interesting things, second-hand speakers, car lights, and all kinds of bells and whistles Simple electronic sound and light items were also sold a lot, and it was indeed a very special "color" electronic product trading place.

Duan Yun had planned to make a subwoofer and conduct door-to-door sales through his own channels, but after taking a turn here today, he found that this place was also very suitable for promoting his new products.

"Comrade, wait a minute!"

Just as Duan Yun was about to ride away, someone behind him suddenly shouted at him.

Turning his head to look, Duan Yun found that the person who called him was the tall young man who had sold 555 just now.

"What's the matter?" Duan Yun asked.

"Thirty pieces, take it!" The tall young man shook the circuit board in front of Duan Yun.

Obviously, the young man didn't sell the board for half a day.

This is also a very normal thing, although integrated chips are very rare in China these years, and they do attract a lot of onlookers, but for amateurs like them, there are few people who know the goods, and the vast majority of enthusiasts do not know the principle of this chip, let alone the circuit technology that designs and uses this chip, coupled with the high outrageous price, it naturally cannot be sold.

"Then tell me, where did you get this circuit board?" Duan Yun asked with a smile.

"I brought it from a small village in the south. The tall one said.

Obviously, Gao didn't want to tell Duan Yun the specific origin of this circuit board.

"That's right. Duan Yun nodded when he heard this.

In fact, there is no need to say it tallly, Duan Yun can also guess how his circuit board came from.

In the 80s, after the reform and opening up of the country, in addition to importing a large number of urgently needed high-tech products and commodities, a large amount of foreign garbage was also introduced.

The reason for this is because it can make up for the shortage of raw materials in some of our country. Of course, the import of these foreign garbage is not the filthy domestic garbage as we imagined, but includes the waste of electronic products, clothing, waste paper, rubber and other aspects eliminated by various developed countries.

In the 90s, many old foreign brands of old electrical appliances in the market flocked to China through this kind of garbage import.

However, at the beginning, the introduction of domestic mainly clothes, plastics, waste paper and rubber, as for the waste electrical equipment is rare, basically from Hong Kong, Hong Kong is a small local place, can not process these electronic products containing heavy metal toxic substances, and then sent to the mainland through some channels.

And this circuit board with chips is mostly selected from those scrapped electronic garbage.

"Thirty" reminded Duan Yun again, he now also wants to get rid of this circuit board as soon as possible.

"Next time I have this kind of chip for me, twenty yuan a piece, I want as many as I want, and I also want other chips that can be used well. Duan Yun took out three pieces of Great Unity and handed them to the tall one and said.

"Done!" said the tall man after taking the money.

Subsequently, the two left their names and contact information, and Duan Yun rode away with the circuit board.