IC for interfacing 7-segment display with attiny85

[kgray9]

Thanks @Wawa

I did forget all that. I knew I was forgetting something .

Yes, thank you, it is 18v max. I got mixed up with the same regulator but for 3v, which has a 30v max.

[ShermanP]

How about the ATTiny2313. A 20-pin chip. Not much flash or ram, but if it's enough you could drive the display directly. But I guess finding any would be a problem, and I don't know about the IDE.

[noiasca]

@kgray9

I am trying to keep it below $4 (display and IC)

and later

I am trying to have everything on one PCB,

and finally a Voltmeter.

I think the Chinese can do this to a small price tag and very small:

3 digit Voltmeter
0,36 inch Voltmeter
4 digit Voltmeter

[GolamMostafa]

@kgray9

What do you all think of this schematic and 3d designs?

Why is the schematic not showing all the 4 digits (LED2, LED3, LED4 are not seen). Would appreciate to see the codes and the procedure of fusing these codes inside the flash. Are you using Arduino Platform or else to develop the control program for your Volt Meter?

Practically, the C1 and C2 capacitors (see Post-5) are needed to be placed as close as possible to the Vcc-pin of MAX7219, which are not seen in your schematic.

[GolamMostafa]

@noiasca

I think the Chinese can do this to a small price tag and very small:

He is not interested to buy but to make himself!

[kgray9]

Below $4 only for the display and display IC. Right now, it is at exactly $4. That entire PCBA cost $8.90.

And definitely no pre-made Chinese garbage.

[kgray9]

@GolamMostafa

Why is the schematic not showing all the 4 digits (LED2, LED3, LED4 are not seen).

I am using easyEDA, so I enter the part number of a piece, and place it onto my circuit. The LED1, LED2, etc. are actually G1, G2, etc.

@GolamMostafa

Are you using Arduino Platform

Yes. I have just started working on the code.

@GolamMostafa

Practically, the C1 and C2 capacitors (see Post-5) are needed to be placed as close as possible to the Vcc-pin of MAX7219, which are not seen in your schematic.

Yeah, I seem to have forgotten all the capacitors .

I am working on fixing it now, will post an updated version soon.

[GolamMostafa]

@kgray9

I am working on fixing it now, will post an updated version soon.

I am closely following your thread and the progress of works.

[kgray9]

Here is an updated version of the schematic:

Does anyone know of any connector that I can place on the PCB, to directly connect multimeter leads?

[kgray9]

How about this for a connector?

24.301 Changzhou Amass Elec | C99097 - LCSC Electronics

[kgray9]

I am making a new topic, because I have a lot more questions for voltmeters, which is not specifically this topic.

So everyone please post here instead.

Voltmeter Questions

Hi all! I am making a voltmeter as explained here: https://forum.arduino.cc/t/ic-for-interfacing-7-segment-display-with-attiny85/947402/ I have a bunch of questions about my voltmeter project. Is a voltage divider a reliable way to read high voltages (i.e. 240V)? Are there alternative ways to read voltage? How would I have my voltmeter read AC voltage, instead of only DC? Does anyone know of any connectors that can be placed on a PCB for an electrical test lead to plug into? ( I suggested o…

[GolamMostafa]

Buy a cheap DVM (less than $5 in my country, Thailand Made) and do the reverse engineering.

[Wawa]

@kgray9

Here is an updated version of the schematic:

Regulator datasheet shows 10uF on output and input of the regulator. You already use an smd regulator, so why not use 2x10uF 1206 ceramic. Smaller, and you don't need the extra 100n either.

Can also use 10uF ceramics on the MAX and ATtiny, to save on space and parts count.
And SMD Schottky diodes instead of through-hole 4007.
Leo..

[kgray9]

Thanks @Wawa for your help

I am trying to keep the soldering difficulty level to the easiest, so I was going for as many through hole parts as possible, even if they take up a lot of space.
The regulator is the only part I couldn't find an equivalent through hole part for.

I'll add the 10µF cap on the regulator.

Can you make any sense out of this switch?

K3-2336D-L1 Korean Hroparts Elec | C223868 - LCSC Electronics

I dropped the temp sensor, and am trying to add a multi-switch, for selecting settings.

[Wawa]

Soldering a 10uF 1206 cap is easier than soldering an SMD regulator.
Space also means a more expensive PCB. Through-hole is last-century.

The switch has a datasheet.
A/B/C is which ones of the eight pins are shorted with the three positions.
Leo..