How to added up a Resistor Value using misc values

[CocaCola]

I have no idea what those jumpers that look like staples were used for, but i have seen them in alot of circuits and designers

If you bothered to read Steve's post he has told you twice now, and if you bothered to Google the answer it would have been described in more detail...

 

[danny davis]

well most of the circuits i have seen I didn't have the schematics to them

So how would i know what they did or what function they had if i didn't have the schematics

 

[(*steve*)]

Essentially a jumper is a piece of wire. It performs no function other than to connect 2 points. It is the same as a trace, a component lead, or any other connection.

The fact that there is a connection may mean something, and you're unlikely yo be able to easily establish that in most cases. It's like looking at some random switch and asking "how do I tell what this does?"

Oh, and I have been reminded that the bare wire "staple looking" jumpers are sometimes used as test points by a colleague who has been inside equipment with them so designated.

 

[danny davis]

I have just seen techs use them to put those color ezhooks probes to measure too

 

[(*steve*)]

Test points come in a variety of styles.

• There are special surface mount loop things that you can attach hooks to.
• There are gold plated pads on the PCB (often for automated testing)
• There are vias that are labelled as test points (that the probe tip fits well into)
• There are bare jumpers
• There are pins or stakes
• And there are points labelled on the schematic that you just have to find on the board (urk)

edit: jumpers are not always (or even often) test points. Don't get hung up on it.

 

[MrEE]

This is a very interesting and long discussion about resistor combinations. The problem of coming up with a value quickly by combining other values is not new, I run into this problem all the time. This is especially true with power resistors. I can't imagine keeping every possible value of 2W and 5W resistors. Pretty soon I'd need a 10-car garage for this.
There are plenty of resistor calculators but what Danny is asking for is a "reverse resistor calculator". There is no way around trial and error here, but that's why we have computers. Every household has one! Why not let a PC do the work. I think an excel sheet application can be created to exactly that. This would work by having the user enter the values of all available resistors into a column of an excel sheet, then enter the desired value and tolerance, and a program would go through all possible R//R and R+R combinations. With more programming code, this can be extended to 3 or 4 resistors. This would be a great project.

 

[CocaCola]

There are plenty of resistor calculators but what Danny is asking for is a "reverse resistor calculator".

I linked to two such 'reverse calculators' in post #19

https://www.electronicspoint.com/ad...-using-misc-values-t249113p2.html#post1473021

 

[MrEE]

Yes, I tried those two calculators. The one from TI works better, the other one requires non-standard value as a target. Anyhow. my idea is that the user can enter a list of resistor values he/she has on hand. The calculator will then try to use these values. there may or may not be a solution. If there is no solution , the calculator will suggest the closest value it can come up with.

 

[CocaCola]

Yes, I tried those two calculators. The one from TI works better, the other one requires non-standard value as a target. Anyhow. my idea is that the user can enter a list of resistor values he/she has on hand. The calculator will then try to use these values. there may or may not be a solution. If there is no solution , the calculator will suggest the closest value it can come up with.

If you stock a complete E series those calculators work just fine, and even not if you stock a few basic values you can get pretty close without much hassle by implementing a few series or additional parallel calculations...

I understand where such a calculator like you suggest might be novel but I don't really see it being of much use for the masses... I have never had an issue getting a 'close enough' value with on hand resistors if need be, for most projects hitting within 5% or 10% is acceptable and that is not hard to do with even basic 10, 100, 1000, 10K and 100K values for prototyping... I always keep a stock of those base 10 values on hand all the time just for this purpose...