Upgrading a laboratory power supply or creating a homemade charger for a car battery is almost impossible without visual monitoring of the output parameters. Chinese ampere-voltmeter is a compact and inexpensive solution that allows you to monitor voltage and current in real time. However, a seemingly simple installation procedure often raises questions among radio amateurs, especially regarding the connection diagram and calibration of readings.
Incorrect switching can lead to failure not only of the measuring device itself, but also of an expensive transformer or power supply controller. In this article we will analyze in detail how to connect the wires correctly, what nuances it has calibration different models and how to avoid common mistakes when integrating an indicator into the body of your device.
Before you pick up a soldering iron, you need to clearly understand that most budget modules require independent power supply for your electronics. Ignoring this fact is the most common reason why the device either does not turn on or shows absurd values. Let's get into the technical details to make sure your project works the first time.
Types of modules and their features
The market is full of various modifications of measuring heads, and the choice of a specific model depends on your tasks. The most popular devices with LED display red, blue or green glow, as well as more modern LCD screens with backlight. The former are highly bright, but can be blinding in the dark, while the latter provide better readability in different lighting conditions.
The key difference between the models is the way the indicator itself is powered. There are two-wire circuits, where the device is powered from the measured voltage, and three-wire circuits, which require a separate source. Two-wire options are easier to install, but often have errors at low voltages (less than 4.5β5 Volts), since part of the energy is spent on operating the display.
Three-wire models such as the popular series DSN-VC288 or YB27VA, provide more stable readings over the entire measurement range. They require thick power wires to measure current and thin wires to supply power to the logic. It is important not to confuse the purpose of the contacts, since polarity is critical here.
- π΄ LED indicators: High brightness, good visibility during the day, but may interfere at night and consume more power.
- π΅ LCD screens: Compact, ability to display additional parameters, lower power consumption.
- β« Hybrid models: They combine the advantages of both types and often have a switchable color scheme.
β οΈ Attention: Cheap two-wire modules can βlieβ at voltages below 20 Volts, since the stability of their internal circuitry depends on the level of the measured voltage.
When choosing a device for your car charger, pay attention to the operating range. Standard models typically measure up to 100 Volts and 10 Amps, which is sufficient for service 12 volt and 24-volt on-board networks. For more powerful stations, you will need to select specialized current sensors.
Necessary tools and preparation
For high-quality installation of an ampere-voltmeter, you will need a minimum set of tools that any car enthusiast or radio amateur will have. The main tool will be a soldering iron with a power of 25β40 W with a thin tip, since the contacts on the indicator board are quite small. Using a soldering iron that is too powerful can cause the traces to peel off.
It is also necessary to prepare pieces of copper wire of different sections. For the power part, through which the main charging or power supply current will pass, you need a wire with a cross-section of at least 1.5β2.5 mmΒ². For the power supply circuits of the indicator itself, thin mounting wires with a cross section of 0.2β0.5 mmΒ² are suitable. Isolation wires must be heat resistant.
Don't forget about the multimeter. It will be needed not only to check the integrity of the circuits, but also for the initial calibration of the readings of the Chinese device, since the factory settings often have an error. Heat shrink tubing and electrical tape will help to neatly arrange the terminals and avoid short circuits inside the case.
βοΈ Preparation for installation
Before starting work, be sure to turn off the power supply and discharge the output capacitors. Residual voltage can be dangerous not only to your health, but also to the sensitive electronics of the measuring module. Check that there is no voltage with the multimeter probes before touching any contacts.
Connection diagram: step-by-step instructions
The connection process depends on the type of module you select. Let's consider the most common option with three groups of contacts: two thick wires for measuring current and voltage, and three thin ones for powering the device itself. Thick wires are usually already soldered into the board or have terminals.
The thick black wire connects to the negative (GND) output of the power supply, and thick red - to the plus (V+) through the load or directly, depending on the design of the current sensor. In some models, thick wires serve only to pass current, and measurement occurs through a shunt inside the housing.
Thin wires are responsible for logic. It is important to follow a strict sequence here:
1. Thin black - a common minus of the indicator power supply.
2. Thin red - power plus (usually 5β30 Volts).
3. Thin yellow (or green) - voltage measuring input.
| Wire color | Function | Where to connect | Section |
|---|---|---|---|
| Thick red | Current/voltage input | Plus power supply output | > 1.5 mmΒ² |
| Thick black | General minus | Minus power supply output | > 1.5 mmΒ² |
| Slim Red | Logic power (+) | Separate source 5-30V | 0.2-0.5 mmΒ² |
| Slim black | Logic power (-) | General minus | 0.2-0.5 mmΒ² |
| Thin yellow | Voltage measurement | Parallel to exit | 0.2-0.5 mmΒ² |
Pay special attention to connecting the yellow (measuring) wire. It must be connected to the point where you want to see the voltage on the screen. If you connect it after the shunt or regulator, the readings will be correct. If before, you will see the input voltage, not the output.
The nuances of connecting a shunt
In some models, the ammeter is connected to the open circuit of the positive wire, and in others - to the negative wire. Carefully study the circuit on the board: if the shunt (copper jumper) is in the path of the thick black wire, then the measurement is negative. By reversing the polarity in such circuits, you can burn out the input circuits of the device.>
Organization of independent catering
One of the most common problems is the lack of a separate voltage source to power the ampere-voltmeter itself. If your power supply is regulated from zero, then when the output is below 4.5 Volts, the indicator will simply go out or start showing chaotic numbers. The solution is independent food.
To implement this circuit, you can use a small step-down board (DC-DC converter) or a separate transformer winding. For example, if you have a 220/24 Volt transformer, you can add a simple linear stabilizer based on L7805 or L7812, which will take power from the main winding to the voltage regulator.
It is important to provide galvanic isolation or a common βgroundβ wire. The minus power supply of the indicator and the minus of the measured circuit must be connected, otherwise the device will not be able to read the data correctly. However, the positive circuits can be separated.
β οΈ Attention: Never apply voltage higher than 30 Volts to the thin power wires of the indicator (for most Chinese models). This will instantly disable the device. Use voltage stabilizers.
If you are making a charger from an ATX computer power supply, then using a line solves the problem +5V or +12V the block itself. Simply connect the thin indicator power wires to the corresponding outputs of the power supply, which are active immediately after switching on, regardless of the main circuit adjustments.
Calibration and adjustment of readings
Chinese instruments often suffer from inaccurate readings, especially at the lower limits of the scale. Fortunately, most models have a built-in calibration system. There are two small potentiometers on the board, usually labeled V-ADJ (for voltage) and I-ADJ (for current).
To set up, you will need a reference multimeter. Apply a known voltage to the output of the power supply, for example, 12.00 Volts, and turn the corresponding screw on the indicator board until the readings match. Carry out a similar procedure with current, loading the power supply with a resistor or lamp.
Some modern models do not have physical screws, but require software intervention through a button on the case. In this case, you need to hold down the button when turning on the power and short presses to select the calibration mode. Detailed instructions for a specific model YN3010 or analogues are best found in the technical data sheet.
Remember that current calibration depends on the shunt resistance. If you replaced a standard shunt with a homemade one made from nichrome wire or a more powerful resistor, the readings will be incorrect without recalculation. Resistance The shunt must strictly correspond to the calculated value for this board.
Typical errors and troubleshooting
Even with careful study of the diagrams, users often make mistakes. One of the most common is an attempt to power the indicator from the circuit being measured at voltages below the start threshold. As a result, with a gradual increase in voltage, the needle or numbers begin to jump until they reach 5 Volts.
Another mistake is using too long and thin wires to connect the current sensor. This introduces additional resistance, which distorts measurements, especially at high currents. The wires from the shunt to the board should be as short and thick as possible.
If the indicator shows voltage, but zero amperes under load, check the integrity of the shunt and the reliability of soldering thick wires. It often happens that when assembling the case, a wire breaks off or a contact comes off. It is also worth checking whether the fuse has blown, if it is provided for in the design.
- π₯ Overheat: At currents above 5 Amps, the board may heat up. Provide ventilation or place the indicator on the housing panel.
- π Accuracy: At low currents (less than 50 mA), cheap shunts may not register the current at all.
- π Interference: Long wires can pick up interference. Twist power wires and use shielding.
β οΈ Attention: If the indicator flashes on and off when connecting, please turn off the power immediately. Most likely, you reversed the polarity or applied a voltage higher than permissible to the logic inputs.
To eliminate flickering of the readings (which often happens when working with switching power supplies), you can solder a small ceramic capacitor with a capacity of 0.1 ΞΌF parallel to the voltage measurement inputs. This will smooth out the pulsations and stabilize the numbers on the display.
FAQ: Frequently asked questions
Is it possible to connect an ampere-voltmeter without a separate power supply?
Yes, if the model is two-wire or can be powered from the measured voltage (usually from 4.5V to 30V). However, for accuracy and stable operation at low voltages, it is better to use a three-wire circuit with an independent source.
Why does the ammeter show current when there is no load connected?
This may be caused by interference from long wires, incorrect zero calibration, or current leakage in the power supply circuit itself. Try twisting the current measurement wires or adding a load resistor to the output.
How to increase the current measurement limit beyond 10A?
To measure large currents, it is necessary to replace the standard shunt with a more powerful one with lower resistance and calibrate the device. You can also use an external shunt by connecting the device in parallel with it.
Can this module be used for a 220V network?
Absolutely not! These modules are designed to measure direct current (DC) or sometimes low frequency alternating current in low voltage circuits. Connecting to a 220V network will lead to an explosion of the device and possible electric shock.