Hey AAC!

I'm making a spiking neural network using hardware as a bit of a challenge for myself, but I've run into a problem with my logic gates. For my synapse update circuitry, I need an IMPLIES gate, and I know how to make one but my version involves the inevitable shorting of my power supply which prevents me from having any other components. Really, I get this problem whenever I make some kind of digital inverter, be it a NOT, a NAND, or my IMPLIES gate. If anybody has designs for inverters that don't involve a direct connection to ground, or manage to avoid shorting the power supply, I'd love to hear it.

Cheers,
microchipsndip

 

Perhaps if you would show how you are trying to implement your gates we might be able to make some useful observations. Otherwise you are relying on the quality of our crystal balls.

 

Hi,
can you show a little bit drawing of that so we can see where to start.

 

Hey!

Thanks for the quick reply. I attached a picture of my circuits for NOT and IMPLIES.

Cheers,
microchipsndip

 

A->B is equivalent to NOT A OR B. Use a NOT gate and an OR gate.

 

kubeek,

I know how logic gates work, what I'm trying to avoid is the ground that comes with the inverter.

Cheers,
microchipsndip

 

I don´t get it. what you have is an RTL gate, and the output is either at 0V or at 2.5V. What do you mean by "the ground that comes with the inverter"?

my version involves the inevitable shorting of my power supply which prevents me from having any other components

Can you show what you mean? So far I don´t see any way the cricuits you show could short the Vcc to ground.

 

kubeek,

The short happens whenever the transistor is turned on. When closed, the transistor creates a route direct from Vcc to ground.

Cheers,
microchipsndip

 

You mean, direct through the resistor? That resistor would be somewhere in the 10k range, which I really wouldn´t call a short. Yes it loads the supply a bit, but really is not that big of a problem.

 

kubeek,

The short happens whenever the transistor is turned on. When closed, the transistor creates a route direct from Vcc to ground.

Cheers,
microchipsndip

How does it do that? You have a resistor between the collector of the transistor and the positive supply rail.

What sizes are the resistors you are using?

Why aren't you just using standard TTL/CMOS logic gates?

 

kubeek & Wbahn,

I'll use CMOS gates, I've got my IMPLIES working. Thanks for the help. I'm still getting a serious drop in voltage when I turn on my transistor though.

Cheers,
microchipsndip

 

Then post a complete circuit with component values, much better than just a blank sketch.

 

kubeek & Wbahn,

I'll use CMOS gates, I've got my IMPLIES working. Thanks for the help. I'm still getting a serious drop in voltage when I turn on my transistor though.

Cheers,
microchipsndip

A serious drop in voltage WHERE???!!!

What is driving your inputs? What are your outputs driving?

Post a COMPLETE schematic, with component values.

 

I'll use CMOS gates, I've got my IMPLIES working. Thanks for the help. I'm still getting a serious drop in voltage when I turn on my transistor though.

That's because your circuit is not correct. Your schematic has no resistor values, so it cannot be analyzed. But given what we know from the last *90 years* of digital logic circuit design , it is fair to say that your design is flawed. If the circuit has a problem with bipolar transistors, it will have the same problem with MOS and CMOS parts. There is no magic here. Your circuit is incorrect, and as long as you keep critical details secret it will stay that way.

ak

 

Once again someone seeks help with a problem but either refuses or is unable to give any reasonable sort of information to those from whom he seeks help!

I am not quite sure why people take this attitude. If you REALLY have something super-secret that you don't want the world to know about, then this is absolutely not the right forum to be looking for help in!

If that doesn't apply, then for heaven's sake give the people who are trying to help you something to go on - and by that I mean EVERYTHING! And if you really don't understand what it is you are trying to do, don't make nonsense statements like: "When closed, the transistor creates a route direct from Vcc to ground", which it clearly doesn't, and only tends to confuse.

I am not having a go at the OP (well, maybe a bit!) just trying to make it easier for people to get answers.

State EXACTLY what it is you are trying to achieve, state CLEARLY how you are trying to achieve it and describe FULLY the problems you are experiencing or the undesirable results you are getting. Then you might get some sensible answers!

Phil

 

its really ammazing

The NOT gate is an electronic circuit that produces an inverted version of the input at its output. It is also known as an inverter. If the input variable is A, the inverted output is known as NOT A. This is also shown as A', or A with a bar over the top, as shown at the outputs. The diagrams below show two ways that the NAND logic gate can be configured to produce a NOT gate. It can also be done using NOR logic gates in the same way.

What "diagrams below"?

Look at the first several posts. For whatever reason, the TS is trying to implement the implication function using RTL (resistor-transistor logic). They haven't provided enough info to determine if this route is a reasonable one to pursue and it has been suggested that they at least consider using off-the-shelf gates. Beyond that we can only accept that their decision to use RTL is reasonable and proceed on that basis.

 

I think that rifat499 is most likely a spammer who is trying to get his post count, the blurb was copied from here http://www.ee.surrey.ac.uk/Projects/CAL/digital-logic/gatesfunc/

 

I think that rifat499 is most likely a spammer who is trying to get his post count, the blurb was copied from here http://www.ee.surrey.ac.uk/Projects/CAL/digital-logic/gatesfunc/

Hmmm.... looks like a definite possibility.

 

I think that rifat499 is most likely a spammer who is trying to get his post count,

I have no idea what this means, so I guess everyone old is noob again.

ak

 

I have no idea what this means, so I guess everyone old is noob again.

ak

In many forums (including this one) there are privileges that members don't have until they get at least so many posts under their belt. For instance, here you can't start a Conversation until you have a certain number of posts. In some forums you can't post any links unless you reach a threshold. Spammers, of course, want to post links. Since most forums don't advertise these settings and since spammers are about volume, many just automatically post garbage in order to get a post count up quickly on the assumption that this will get them link-posting privileges. Keep in mind that most of the time these are brain-dead bots using brute force techniques (though the sophistication of some of these bots is pretty amazing).