| Electronics > Beginners |
| 74LS14 testing circuit pls |
| << < (10/15) > >> |
| Chriss:
Ian.M: Thanks for this nice explanation, I really appreciate it. I will definitively switch to the 74HC/HCT series IC's. ebastler: When I say „this type of IC“ has worked for me in the past, I mean this hexagon Schmitt trigger IC's but from other manufacturer. I never faced with this brow casing IC. I have experience with 74xx series IC's but from other manufacturer. amyk: No, the bottom didn't looks like on the link. The bottom is simple brown plastic like the upper side. |
| Chriss:
Ok, today I got new IC's but now SN74S14N in black package... Please give me suggestion how to correct breadboard this IC. In the past I used the 1. circuit from my schematic above. I read somewhere on the net does all the not used input pins should be pull-up or down. I never did that before and I never killed any IC this type of Schmitt trigger. But now I'm a bit afraid and wish to change things if I need to make my circuits better. What would be your simplest setup for a quick test on breadboard the SN74SL14N? Thank you. |
| iMo:
Based on the package and type of font used it is an old Soviet chip (most probably an export marking).. The former eastern countries produced 74xxx series as well, they used black packages (with different form and fonts used), however. This is the simplest test you may try: http://www.learningaboutelectronics.com/Articles/7414-schmitt-trigger-oscillator-circuit.php You may use any resistor 1k-100k and capacitor 10nF-10uF with your test. You may wire the inputs of the other free inverters to the oscillator's output and observe their outputs - you have to see pulses as well.. |
| Ian.M:
Are you sure about that part number? Google doesn't return *ANY* datasheets for SN74S14N or even 74S14. If that's what's on them, odds are they are fakes. IMHO its more likely you've got SN74LS14N chips. Your circuit n.o. 1 or my circuit from reply #21 will do to test them, one gate at a time. Don't leave them running for a long time on my circuit - it pushes them too close to their limits. Bipolar TTL (all types) inputs float high well enough that you can leave unused gates' inputs floating when breadboarding. However the recommendation for the final build is to pull up to Vcc via a 1K resistor. You can often group several unused inputs to one resistor. Strictly speaking its only original 7400 series TTL that you *had* to use a pullup resistor for to avoid latchup if the input experienced a spike on the Vcc rail. One generally avoids grounding unused inputs unless its required for the logic function, as that consumes extra current. Don't leave spare inputs of used gates floating - that can result in big trouble with glitches when another pin on the same chip changes state. CMOS is *MUCH* easier - just tie the input direct to either rail AT THE CHIP - it wont waste current and it wont latchup. |
| PA0PBZ:
In the same post he calls it a SN74SL14N so my bet is a keyboard problem. |
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