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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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. Therefore, both diodes have to have a logic 1 in order to allow the output to rise to a logic 1. This current draw will pull up the clock input of the 74LS to a logic 1 momentarily. When the capacitor stops charging up, the 22K pull-down resistor pulls the clock input down to a logic 0. 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.

I think if the 74LS operated on a rising edge, the circuit might work without the capacitor and resistor. A colon indicator can be added by using the 1Hz pulse off pin 5 of U3a. It took some experimentation before I could get the signals to work correctly between the chips.

None of the other digits have this trait. This falling edge triggers the 74LS to advance one more time. I realized a design flaw when I finished the clock. The datasheet says the chip was designed to have a strong tolerance for noise, and there is no mention of this in dayasheet 74LS datasheet.

The two diode AND gate, one connected to segment F and one to the inverted segment G, will produce a logic 1 only when segment F is on and segment G is off. I originally planned on using a Mostek MK 6-digit clock chip that multiplexes the digits.


Dual 4-Bit Binary Counter

The other segments for the zero are all wired together and switched on and off by a flip-flop. If you used 60Hz from mains and fed it into thethere was still some noise passing through that would make the 74LS’s go haywire. Click here for the schematic diagram of the four B nixie clock. 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 planned on placing the neon bulbs under each digit, so if you’re plain then look at the Bs and if you’re a geek then look at the binary below. I had to use a very small 8-volt transformer that just barely fits inside the case to supply the low voltage power.

Without the K resistor and 0. 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 I never had a problem with this in my other two clocks that run off mains, and I discovered the reason after taking a closer look at the datasheets.

I came to a point where I thought I had gotten the design, so I proceed to build the clock. 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.

74LS Datasheet(PDF) – Hitachi Semiconductor

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. Even dataeheet seconds display can be added to this circuit, simply add two more decoder chips on U3b and U4a. I personally prefer hour mode. This would’ve been a bad waste of chips, so I decided to do the remaining logics the old school way This configuration helped solve the problem.


These versatile nixie tubes can allow for a variety of characters and digits with different styles.

74LS Fairchild Semiconductor, 74LS Datasheet

datasheeh 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. I used the for the first stage to divide 60Hz to 10Hz. So much for the dtaasheet design that used all of the chips wisely. As you can see in the schematic, the portion marked in blue uses two AND gates and one inverter gate.

The inverter using a transistor and resistor changes the “off” G into a logic 1 for the AND gate. However, that didn’t work out due to complications with the circuitury and the amount of room in the clock case I dahasheet. One advantage to use what is essentially a binary clock with 7-segment decoders is to have small neon bulbs or LEDs driven directly from the BCD outputs.

The “C” that is switched on to make a dxtasheet comes on when the clock is in the single digit hours. I found a “trait” of the 7-segment zero digit, segment F has to be on and segment G has to be off. When the clock goes to 10, 11, or 12, the “C” is turned off so the digit 1 appears. Recall that the 74LSs trigger on a falling edge, not a rising edge.

Then the DRL output goes high so the capacitor starts to charge up. There, you have it, a “double” pulse to get rid of the 00 hours.