NOR Gate circuit - Can it be built with floating inputs - Page 2 - Electronic Circuits Projects Diagrams Free

DamoRC · 28th June 2008, 02:32 PM

Thanks Roff but no can do. Firstly because the goal was to not interfere with the stock electronics making this a "plug and play" type add-on and secondly, and more importantly, because I would have no idea where to start on the stock electronics to achieve such a result.
For the time being I am going to solder up what I have. Might try again at a later time with a H-bridge driver.

Thanks again

Roff · 28th June 2008, 02:59 PM

Quote:

Originally Posted by DamoRC

Thanks Roff but no can do. Firstly because the goal was to not interfere with the stock electronics making this a "plug and play" type add-on and secondly, and more importantly, because I would have no idea where to start on the stock electronics to achieve such a result.
For the time being I am going to solder up what I have. Might try again at a later time with a H-bridge driver.

Thanks again

The pullups could be added to the A and B inputs of your new circuit. Don't they connect directly to the outputs of the stock H-bridge?

DamoRC · 28th June 2008, 05:29 PM

Quote:

Originally Posted by Roff

The pullups could be added to the A and B inputs of your new circuit. Don't they connect directly to the outputs of the stock H-bridge?

Yes they do.

Pulling both inputs high as the default condition of the circuit would mean the coast condition would be two highs. Let me brood on this for a while to see if I could make that work. Thanks for the suggestion.

Roff · 28th June 2008, 07:38 PM

Quote:

Originally Posted by DamoRC

Yes they do.

Pulling both inputs high as the default condition of the circuit would mean the coast condition would be two highs. Let me brood on this for a while to see if I could make that work. Thanks for the suggestion.

If you do a truth table, you'll see that the logic is really simple. If you need help with the truth table, let us know.

DamoRC · 28th June 2008, 08:25 PM

When you say "truth table" do you mean:
A high B high - coast
A high B low - forward
A low B high - reverse
A low B low - brake
?

Roff · 29th June 2008, 12:24 AM

Quote:

Originally Posted by DamoRC

When you say "truth table" do you mean:
A high B high - coast
A high B low - forward
A low B high - reverse
A low B low - brake
?

I mean the complete truth table to control each individual MOSFET, as below.

DamoRC · 30th June 2008, 04:42 PM

Okay - so what I need to do now is come up with a set of logical operations that both A and B go through to deliver the desired outputs at W, X, Y and Z. I'll get back when I have the answer figured out.

Cheers.

Roff · 30th June 2008, 05:47 PM

Quote:

Originally Posted by DamoRC

Okay - so what I need to do now is come up with a set of logical operations that both A and B go through to deliver the desired outputs at W, X, Y and Z. I'll get back when I have the answer figured out.

Cheers.

That's correct, and the logic functions are really simple. Don't waste too much time on them unless you want the learning experience. We can post them here.
PS The simplest way is probably to use gates in the CD4000 logic family. Keep in mind that you will have to follow each one with a level translator, which will generally also be a logical inverter.

DamoRC · 4th July 2008, 08:15 PM

Roff - thanks. For now I am going to go without a brake. I completed the circuit (version 2) and thus far it seems to work fine.

I will revisit the brake function at a later date and learn smething about the logic family that you have suggested.

Again thanks for all of your help

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28th June 2008, 02:32 PM	(permalink)
DamoRC	Thanks Roff but no can do. Firstly because the goal was to not interfere with the stock electronics making this a "plug and play" type add-on and secondly, and more importantly, because I would have no idea where to start on the stock electronics to achieve such a result. For the time being I am going to solder up what I have. Might try again at a later time with a H-bridge driver. Thanks again

28th June 2008, 08:25 PM	(permalink)
DamoRC	When you say "truth table" do you mean: A high B high - coast A high B low - forward A low B high - reverse A low B low - brake ?

30th June 2008, 04:42 PM	(permalink)
DamoRC	Okay - so what I need to do now is come up with a set of logical operations that both A and B go through to deliver the desired outputs at W, X, Y and Z. I'll get back when I have the answer figured out. Cheers.

4th July 2008, 08:15 PM	(permalink)
DamoRC	Roff - thanks. For now I am going to go without a brake. I completed the circuit (version 2) and thus far it seems to work fine. I will revisit the brake function at a later date and learn smething about the logic family that you have suggested. Again thanks for all of your help