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74LS, 74LS Datasheet, 74LS Dual 4-bit Binary Counter Datasheet, buy 74LS, 74LS pdf, ic 74LS 74LS SN74LSNSR. ACTIVE. SO. NS. Green (RoHS. & no Sb/ Br). CU NIPDAU. LevelC-UNLIM. 0 to 74LS SNJ54LSFK. Each of these 74LS monolithic circuits contains eight masterslave flip-flops and additional gating to implement two individual four-bit.

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Recall that the 74LSs trigger on a falling edge, not a rising edge. As you can see in the schematic, the portion marked in blue uses two Dahasheet gates and one inverter gate.

The datasyeet triggers on the rising-edge. This falling edge triggers the 74LS to advance one more time. The inverter using a transistor and resistor changes the “off” G into a logic 1 for the AND gate.

74LS Datasheet PDF – Texas Instruments

However, after trying the chip out with two nixies, I found that the brightness was not very strong. The reason is because if segment F is off or segment G is on inverter produces a logic 0then the diode s will pull down the output to ground and produce a logic 0.

It took some experimentation before I could get the signals to work correctly between the datashset. When the clock goes to 10, 11, or 12, the “C” is turned off so the digit 1 appears.


However, I had to delay the pulse from the DRL until the 10 minutes counter finished sending its clock pulse to the 1 hours counter. I also found out that the circuitry draws a good amount of current so I couldn’t simply obtain low voltage from the voltage doubler and regulate it for the low voltage supply like I could in my first two nixie clocks. I realized a design flaw when I finished the clock.


I figure since the latter was normally used in older computer systems, the power supply and input signals are expected to be well-filtered and free of noise. I designed the clock circuitury hoping to achieve a perfect design that uses all of the logic available in all of the chips I would need.

For this clock, I decided to go with the traditional 7-segment display to show the time.

74ls393 datasheet pdf

datasheft For the ten hours, I didn’t want to waste another 74LS and chip just to display zero and one. I had to use a very small 8-volt transformer that just barely fits inside the case to supply the low voltage power. Assembly and Testing Completed view of assembly bottom view Back to Top.

Therefore, both diodes have to have a logic 1 in order to allow the output to rise to a logic 1. I originally planned on using a Mostek MK 6-digit clock chip that multiplexes the digits.

After discovering this noise problem, I swapped them around. I 7ls393 a “trait” of the 7-segment zero digit, segment F has to be on and segment G has to be off.

I figured that with the in the front, it would buffer out more of the noise and generate a cleaner clock pulse for the 74LS chips. Below is the pinout of the B nixie: I think if the 74LS operated on a rising edge, the circuit might work without the capacitor and resistor.


74LS Dual 4-Bit Binary Counter :: Micro JPM

After overcoming the noise problem with the 74LSs in the clock, I learned of another minor design issue. I came to a point where I thought I had gotten the design, so I proceed to build the clock. Click here for the schematic diagram of the four B nixie clock. The 74LS clock input triggers on a falling-edge of a square wave when the square wave signal drops from a logic 1 to 0.

There, you have it, a “double” pulse to get rid of the 00 hours. In the process of constructing the clock, I found that these chips were extremely sensitive to noise. I was faced with the problem of the clock starting at 00 hours, but the clock does count nicely to 12 and resets back to So much for the “perfect” design that used all of the chips wisely.

Even a seconds display can be added to this circuit, simply add two more decoder chips on U3b and U4a. Anyway, on to the pictures.