Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated. Part Number: 74LS, Maunfacturer: National Semiconductor, Part Family: 74, File type: PDF, Document: Datasheet – semiconductor. 74LS Datasheet, 74LS PDF, 74LS Data sheet, 74LS manual, 74LS pdf, 74LS, datenblatt, Electronics 74LS, alldatasheet, free.
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Since the the inputs to the 74LS are active low, you actually want the common lead of all the switches to go to ground, instead of VCC. This is why the outputs of the encoder are always high — if the switches are off, the floating inputs act as high inputs, and 74ls14 a switch is on it is also driving the input high.
So there is no way to drive any of the inputs low. Besides tying the common lead of the switches to ground, I would also connect 4. This way it will work for both types of chips.
datashewt With your DIP switch connected as described you will need to provide a way for the inputs of the decoder chip to go low when the switch is off. That said, when using a chip like the LS you may want to rearrange the connections as shown below and use pullup resistors to establish the high levels on the inputs to the chip.
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74LS Datasheet, PDF – Alldatasheet
If it has 10 switches, then I assume you mean pin, not pin. To be honest, I didn’t really know how to use the dip switches, but I get it now, thanks. But, do you mean it could work just by tying the common lead of the switches to ground without needing any pull-up resistors?
So you can just move your common lead from VCC to ground and try it. I’d still add the pull-ups though. Second, make sure your switches are all off to begin with, and then turn only one on at a time if you do turn on more than one, there is a table in the 74LS datasheet which will indicate what the output should be.
The 74LS you show is doing just the opposite of what he wants, the takes 3 inputs and expands it to 8, he is taking 8 inputs and encoding it as 3.
In any case, in your example only inputs A, B and C should come from switches. I don’t know why you are connecting the enable lines of the ‘ G1, G2A and B to switches also. I read the question in dyslexic manner. Sign up or log in Sign up using Google.
74LS Datasheet PDF –
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