A recent addition to my standard breadboard setup in two small DC voltmeters. I have found it beneficial to have meters committed to the breadboard to give instant feedback on the circuit I'm working on.
Other items on my breadboard ...
Battery powered, + and - 15 V from AA battery packs.
+5 V regulator, LM78L05 with a 2N4403 bypass transistor, so I have about 250 mA available.
Two adjustable voltage sources, + to - 12 V, LM358 and trimpots, with the option of adding buffer transistors on the output.
A simple inverter circuit, LF356 running from + and - 15 V to invert a negative voltage to positive so the meter can read it. The meters do not read negative voltages. What do you want for $5.00 meters?
One 2.5" x 6.5" breadboard mounted to a replaceable basswood plate.
All this in a 9" x 12" wooden box which gives me ample top space for attachments and projects and storage space inside for batteries and other breadboards.
I have a shoebox of doodads and attachments (signal generators, digital and analog add-on circuits built up over the years. Battery powered 60 Hz sine wave source, signal generators ...).

I prefer plain wire jumpers over the high quality jumper wires with connectors. The plain wires just take up less space on the board.

In retrospect I might advise to spend a little more and get meters that read positive and negative voltages, and more current on the +5 V supply. Maybe a separate voltage source for that. Maybe two 18650 batteries to drive that. But that would just be using what I have on hand, no other reasons.

AC wall wart power packs? I have them available. Literally, I have hundreds. I can throw together most any voltage or current I need for a project in short order.

(edited to add...)
In the picture attached the small breadboard at the top is power stuff (two variable supplies and +5 Volts). the TO-39 case is the LF356 inverter if I want to measure negative voltages on one of the two meters.
The small breadboard on the right is a current project. "760" is the design number so I can reference the schematic if I need to.
I use the main breadboard for early development of circuits. Once I get a circuit close to working I put it on a small breadboard with dedicated parts and wires. Seldom does a circuit get developed to be committed to a PC Board and/or a box.

 

A recent addition to my standard breadboard setup in two small DC voltmeters. I have found it beneficial to have meters committed to the breadboard to give instant feedback on the circuit I'm working on.
Other items on my breadboard ...
Battery powered, + and - 15 V from AA battery packs.
+5 V regulator, LM78L05 with a 2N4403 bypass transistor, so I have about 250 mA available.
Two adjustable voltage sources, + to - 12 V, LM358 and trimpots, with the option of adding buffer transistors on the output.
A simple inverter circuit, LF356 running from + and - 15 V to invert a negative voltage to positive so the meter can read it. The meters do not read negative voltages. What do you want for $5.00 meters?
One 2.5" x 6.5" breadboard mounted to a replaceable basswood plate.
All this in a 9" x 12" wooden box which gives me ample top space for attachments and projects and storage space inside for batteries and other breadboards.
I have a shoebox of doodads and attachments (signal generators, digital and analog add-on circuits built up over the years. Battery powered 60 Hz sine wave source, signal generators ...).

I prefer plain wire jumpers over the high quality jumper wires with connectors. The plain wires just take up less space on the board.

In retrospect I might advise to spend a little more and get meters that read positive and negative voltages, and more current on the +5 V supply. Maybe a separate voltage source for that. Maybe two 18650 batteries to drive that. But that would just be using what I have on hand, no other reasons.

AC wall wart power packs? I have them available. Literally, I have hundreds. I can throw together most any voltage or current I need for a project in short order.

Parts on hand?
I've been doing this for decades so my inventory list is thousands of items long. Resistors? almost every 1/4 Watt 5%, dozens of each. Capacitors, not that complete but I usually can work a project around what parts I have on hand. ICs? Most TTL and CMOS devices. Diodes? )1N4148, 1N6263, 1N270 and an assortment of popular Zeners. Transistors? 2N3904, 2N3906, 2N4401, 2N4402, 2N7000, BS170, BS250 and an assortment of many others.
164 drawers to keep parts in. 9 file Nine 9" x 11" parts bins that fit nicely into a file cabinet. Maybe two dozen plastic shoe box size containers for wall warts and stuff too big for drawers.

Inventory kept in Excel.

 

A recent addition to my standard breadboard setup in two small DC voltmeters. I have found it beneficial to have meters committed to the breadboard to give instant feedback on the circuit I'm working on.
Other items on my breadboard ...
Battery powered, + and - 15 V from AA battery packs.
+5 V regulator, LM78L05 with a 2N4403 bypass transistor, so I have about 250 mA available.
Two adjustable voltage sources, + to - 12 V, LM358 and trimpots, with the option of adding buffer transistors on the output.
A simple inverter circuit, LF356 running from + and - 15 V to invert a negative voltage to positive so the meter can read it. The meters do not read negative voltages. What do you want for $5.00 meters?
One 2.5" x 6.5" breadboard mounted to a replaceable basswood plate.
All this in a 9" x 12" wooden box which gives me ample top space for attachments and projects and storage space inside for batteries and other breadboards.
I have a shoebox of doodads and attachments (signal generators, digital and analog add-on circuits built up over the years. Battery powered 60 Hz sine wave source, signal generators ...).

I prefer plain wire jumpers over the high quality jumper wires with connectors. The plain wires just take up less space on the board.

In retrospect I might advise to spend a little more and get meters that read positive and negative voltages, and more current on the +5 V supply. Maybe a separate voltage source for that. Maybe two 18650 batteries to drive that. But that would just be using what I have on hand, no other reasons.

AC wall wart power packs? I have them available. Literally, I have hundreds. I can throw together most any voltage or current I need for a project in short order.

(edited to add...)
In the picture attached the small breadboard at the top is power stuff (two variable supplies and +5 Volts). the TO-39 case is the LF356 inverter if I want to measure negative voltages on one of the two meters.
The small breadboard on the right is a current project. "760" is the design number so I can reference the schematic if I need to.
I use the main breadboard for early development of circuits. Once I get a circuit close to working I put it on a small breadboard with dedicated parts and wires. Seldom does a circuit get developed to be committed to a PC Board and/or a box.

Okay, I quickly discovered another problem with my $5 voltmeter. It only measures voltages referenced to ground. No problem. I already had an op amp as an inverter. I just modified it slightly to be a differential amplifier with a gain of 1. Now I can use it as an inverter or to measure differential voltages.
No real reason for using the LF356. I just had a few that were very low offset and low noise.
Precision is tolerable but not professional quality. About 0.02 V off at a 1 Volt reading.