Expanded scale volt meter

Thread Starter

Ian Harris

Joined May 4, 2016
26
@MisterBill2 Had to laugh. I worked in IT for decades, and learnt very early in my career to use a pencil! I hardly ever used a pen. People sometimes asked me why, and my response was always "because there's a rubber on the other end!"
@crutschow you're right, I could figure it out if I put my mind to it I guess, but I'm a lazy sonofa so I always look for the solution that requires a) the least work, and b) the least thought. Call it a personality flaw. ;-)
 

MrSalts

Joined Apr 2, 2020
711
I always look for the solution that requires a) the least work, and b) the least thought.
Then you've come to the wrong place. Over-thinking, over-specified, overtly exacting with a cost-optimized bill-of-materials is the common goal here (no matter how much work it takes - including learning to write code, buying a programmer to flash a microcontroller or order 10,000 pieces to meet minimum order quantities for a one-off DIY project).
 

Thread Starter

Ian Harris

Joined May 4, 2016
26
Well, haven't I had fun trying to learn to use Fritzing. Tried the "piece of paper" approach and ended up with something that looks right to me, but thought using Fritzing might be better.
I have a piece of PCB that's designed to have a DIP package soldered down the middle with small strips radiating out from each side. Underneath the package there are two rails running the full length, and another pair on one side. I'm sure you are all very familiar with this setup.
Anyway, the plan now is to use this thing to mount my four components on. Maybe something like this?

1635307855062.png

The cunning plan is that the left hand vertical rails correspond to the two sides of the meter, and the two on the right are for the battery. The tabs (that would normally be soldered to the legs of the DIP package) are used to mount the other components. Fritzing wouldn't let me modify the yellow lines, but at least they are connected to the right things (I think...) I don't know why the labels are placed so far away from the components. I have not yet discovered how to move them (or rotate them)...

Does this look right?

Thanks,
Ian
 

crutschow

Joined Mar 14, 2008
28,155
R1 should be 47kΩ.
I've added a 2k trimmer pot in series with the resistor which has now become a 47k as recommended in a previous post.
Where did you get that value (you show 470k on the schematic)?
With the 4.7V Zener you show, R1 should be about 800Ω.

And the 4.7V Zener will give a meter zero reading at a battery voltage of about 5.2V.
(Why did you select a 4.7V Zener?)
 
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Thread Starter

Ian Harris

Joined May 4, 2016
26
@crutschow thanks for the feedback.
I selected the first Zener that popped up in Fritzing's menu. I didn't know it was a 4.7V one. The one I have is a 5.1v one.
You're right about R1, it should be 47k.
I've tidied up the diagram a bit. I've discovered how to move and rotate the labels so it's a bit more readable now. The only non-obvious bit is that the positive of D1 is connected to one end of R1.
1635471439644.png

;-) Ian
 
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