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We knew BSIDE only as a manufacturer of multimeters. Until we received a copy of this brand's I8305 power supply with a request to test it thoroughly. We hereby do so. |
Introduction to BISIDE's I8305
A series of three
The I8305 is the least expensive member of BSIDE's I8 series of lab power supplies. This family consists of:
- I8305: 30.0 V ~ 5.0 A, no USB control
- I83010: 30.0 V ~ 10.0 A, with USB control
- I84020: 40.0 V ~ 20.0 A, with USB control
The cheapest model I8305 costs about € 75.00 and provides enough voltage and current to satisfy the average electronics hobbyist. The power supply has three presets that you can set in the menu and then recall by pressing the '1', '2' or '3' buttons. If required, the power supply starts up with zero volts between the output terminals. After choosing one of the presets or setting a different output voltage and current with the buttons and/or the rotary knob, you must press the 'OUTPUT' button to make the voltage appear between the output terminals. You can set overvoltage protection 'OVP' and overcurrent protection 'OCP'. This means that the power supply switches off if, for whatever reason, the voltage at the terminals or the current supplied become greater than the set values. You can disable these two functions if necessary.
The 'U/I' button allows you to either set the desired output voltage or current. The 'OVP/OCP' button has the same function for the overvoltage and overcurrent values.
The I8305 has an additional USB-A output that carries a DC voltage of 5.0 V that you can load up to 2A. The two 4 mm banana plug sockets are both not connected to the chassis. There is no third socket that allows you to ground either output.
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| BSIDE's I8305 lab power supply. (© 2024 Jos Verstraten) |
Announced features that do not exist
Several vendor product pages claim that this range of power supplies has a USB connector on the back that allows you to control the power supply with the PC. However, this does not apply to the I8305! The same pages also state that the power supply gives an audible signal if you short the outputs or if an 'OVP' or 'OCP' condition occurs. This may be true for its more powerful brothers, but at least the I8305 does not have this feature.
The display
The lab power supply I8305 has a multi-colour display measuring 55 mm by 42 mm with a resolution of 320 by 240 pixels. Unfortunately, even BSIDE could not resist the temptation to cram this display with information that is rather useless and makes it difficult to read the useful information. For instance, we find it rather superfluous that in the top left corner, where 'OFF' appears in the image below, the conditions 'OVP' or 'OCP' are listed. It would have been much clearer if these letters appeared in green or in red on the display to the left of set values. Also, the brand and type names and the fact that this device is a 'Programmalbe DC Power Supply' (note the spelling error!) should not have appeared on the display as far as we are concerned. Moreover, we wonder if anyone needs the indication of the number of seconds the power supply is on (under the 'DC', also quite redundant).
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| The overstuffed display of the I8305. (© 2024 Jos Verstraten) |
The rear of the enclosure
About half of the rear is taken up by the exhaust vents of the built-in fan. This is not 'intelligent', as the manufacturer claims. It always turns on if the power supply provides more than 2.5 A, even when cold. For smaller currents, however, the fan does react to the temperature of the internal heatsink. Curiously, you will also find a mains voltage selector switch. Most switched-mode power supplies do not have this. The earthed C14 Euro input for the mains cable is of excellent quality and contains a 5 mm by 20 mm glass fuse.
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| The back of the enclosure. (© 2024 Jos Verstraten) |
The scope of delivery
In addition to the power supply, the package contains:
- A high-quality earthed mains cable
- A thick two-wire connection cable for the output voltage
- A three-page manual in English
The specifications
According to the manual, the I8305 meets the following specifications:
- Output voltage: 00.00 V ~ 32.00 V
- Resolution voltage setting: 10 mV
- Voltage setting accuracy: better than [0.1 % + 5 digits]
- Output ripple: less than 10 mVrms
- Output stability: better than [0.1 % Vmax + 5 mV]
- Output current: 0.000 A ~ 5.100 A
- Resolution current setting: 1 mA
- Accuracy of current setting: better than [0.1 % + 10 digits].
- Presets: 3
- Over-voltage protection (OVP): yes
- Over-current protection (OCP): yes
- Over-temperature protection (OTP): yes
- Overload protection (OPP): yes
- Cooling: controlled air cooling
- USB output: 5.0 V ~ 2.0 A
- Supply voltage: 220 Vac ±10 % ~ 50 Hz or 110 Vac ±10 % ~ 60 Hz
- Dimensions: 15.5 cm x 8.0 cm x 23.5 cm
- Weight: 1.46 kg
The electronics in the I8305
Removing eight bolts
The metal housing consists of a U-shaped lower part to which a higher U-shaped upper part is bolted. After removing eight bolts, you can remove that upper part and the interior of the power supply emerges. That consists of one large main vertical PCB and three small PCBs attached to the bottom and front panel of the power supply. The internal construction makes a bit of a chaotic first impression, but a closer look reveals that the device is rather professionally put together after all.
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| The internal of the I8305 power supply. (© 2024 Jos Verstraten) |
All wiring connected to the mains is fully insulated with heatshrink tubing. The heavier components on the PCB are glued in place. The PCB traces that carry the large output current are additionally tin-plated. Three power semiconductors are soldered to the back of the vertical PCB and are attached to an aluminium heatsink. The cooling fingers of this heatsink are close to the fan. There are insulation slots at strategic locations on the PCB. Although the inverter supplying the 5 V USB voltage draws its primary voltage from the main power supply, it is otherwise completely isolated from it. A large and sturdy double-folded shunt is used as the current sensor. Primary smoothing is provided by two 330 μF and 200 V electrolytic capacitors connected in series.
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| The PCB supplying the 5 V USB power supply. (© 2024 Jos Verstraten) |
Working with the I8305 power supply
Switching on the device
You can use the menu to set the power supply so that after switching on, the device always enters standby mode, i.e. without voltage on the output. You can clearly see this by the red 'OFF' indication at the top left of the display. Of course, the two large white and yellow displays show the voltage and current settings that have been stored in memory.
Setting voltage and current
Press the 'U/I' key to switch between setting the voltage or current. You can see which setting is active because one of the displays to the right of the word 'SET' gets a blue background. Use the cursor keys '◄' and '►' to select one of the four digits. Using the cursor keys '▼' and '▲', set the value of that digit. By the way, you can also do this by turning the circular knob. You will then be able to continuously decrease or increase the output voltage with a resolution of 10 mV.
In an identical way, you can set the value of the constant output current.
The two values of voltage and current are kept in memory.
Activating the output
Press the 'OUTPUT' button. The selected voltage appears between the output connectors. The red indication 'OFF' at the top left of the display is replaced by a green 'CV' (constant voltage mode) or 'CC' (constant current mode).
Setting 'OVP' and 'OCP'
Select the parameter to be set using the 'OVP/OCP' button. Setting the desired value proceeds as described in setting the output values. If the power supply delivers a higher voltage or current than set here, the power supply goes to standby and the indications 'OVP' or 'OCP' appear on the top left of the display.
The 'MENU' button
This button becomes active only when you have switched the power supply to 'OFF' mode. The picture below shows what the menu of this power supply has to offer. You use the cursor keys '◄' and '►' to select one of the options. You set the option using the rotary knob and/or the cursor keys '▼' and '▲'.
Setting the 'Power On Output' option to 'ON' or 'OFF' ensures that the power supply does or does not provide output voltage after operating the mains switch. We strongly recommend that you select the 'OFF' option here!
The 'Address' and 'Baud' options are quite funny in a power supply that cannot communicate with the outside world. After all, that is reserved for the two more expensive power supplies in this series.
With 'M1-U', 'M1-I', 'M2-U', 'M2-I', 'M3-U' and 'M3-I', you obviously set the constant voltage and current of the three presets.
What the 'AdjCode' option means is not clear to us, the manual does not mention it at all.
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| The menu settings on the display. (© 2024 Jos Verstraten) |
Testing the BSIDE I8305
The accuracy of the voltage setting
We connected our multimeter 8842A from Fluke to the outputs and set the unloaded power supply to various output voltages. The table below shows the real values of the unloaded output voltage. The accuracy is excellent, even when set to 1.00 V, the power supply delivers an exact voltage.
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| The accuracy of the output voltage setting. (© 2024 Jos Verstraten) |
Accuracy of current setting
We short-circuit the outputs of the power supply with our multimeter ET3255 from EastTester switched to 12 Adc and set the output current to various values. The measurement is performed at an output voltage of 5.00 V. The results are summarised in the table below and are again excellent.
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| The accuracy of the output current setting. (© 2024 Jos Verstraten) |
Output stability at 5.00 V output voltage
Output stability defines the constancy of the output voltage as a function of the load current. This parameter is not necessarily the same at every output voltage, so it must be tested at various voltages. Naturally, the current is set to the maximum value of 5.2 A. We start at 5.00 V, the results are shown in the table below. The power supply is connected to an adjustable load type EBD-A20H. On the output are of course the Fluke 8842A, a Philips PM2454B mV meter and our oscilloscope XDS2102A from OWON. The mV meter and oscilloscope measure and observe the ripple voltage on the output voltage of the power supply.
The voltage difference between zero and full load is only 49.4 mV. Using ohm's law, you can then immediately calculate the internal dynamic resistance of the power supply. Indeed, a voltage drop of 49.4 mV at a current variation of 5 A yields 9.88 mΩ.
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| Output stability and ripple at 5.00 V output voltage. (© 2024 Jos Verstraten) |
The ripple at 5.00 V and 5.000 A
The previous table shows that the ripple is lower than what the specifications promise. What is noticeable is that the ripple has a very smooth curve, see the oscillogram below. The narrow irregular spikes we have seen in several other cheap switched-mode power supplies are completely absent here.
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| Output ripple at 5.00 V voltage and 5.0 A current. (© 2024 Jos Verstraten) |
Output stability at 12.00 V output voltage
We repeat the above measurements, but now with the output voltage set to 12.00 V. The results are again summarised in the table below. The voltage drops by 66.4 mV, corresponding to an internal dynamic resistance of 13.28 mΩ. The shape of the ripple is similar to this at 5.00 V.
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Output stability and ripple at 12.00 V output voltage. (© 2024 Jos Verstraten) |
Output stability at 29.00 V output voltage
Why tested at 29.00 V and not at 30.00 V? Because our adjustable load EBD-A20H protests at 30.00 V with 'input voltage too high', but works diligently with one volt less. Even at a set current of 5.0 A, the load fails. The device will not draw this current from the power supply, even though the expected power is within specifications. OK, back to the I8305! The voltage drop is now 50 mV, good for an internal dynamic resistance of 12.5 mΩ. Even at this output voltage, the ripple resembles this one at 5.00 V.
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| Output stability and ripple at 29.00 V output voltage. (© 2024 Jos Verstraten) |
Input stability at 29.00 V and 4,000 A
This parameter defines the constancy of the output voltage when the input voltage of the power supply varies. So our variac is taken off and the output voltage is measured when the mains voltage is varied between 170 Vrms and 250 Vrms. The results are again summarised in a table. This shows that the input stability from a mains voltage of 190 Vrms onwards is excellent. The output voltage remains constant!
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| Input stability at a mains voltage between 170 V and 250 V. (© 2024 Jos Verstraten) |
Long-term stability at 5.00 V and 5.00 A
In this test, the power supply, cooled to room temperature, is subjected to a maximum load of 5.0 A at 5.00 V output voltage and it is measured how stable the output voltage remains as a function of time. This heavy load causes the power supply to heat up internally and the question is how well the electronics are designed to compensate for the output voltage drift due to this heating. The results are again summarised in the table below. As these data show, the maximum voltage drift is only +6.2 mV and the output voltage remains stable after about 30 minutes.
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| The long-term stability at 5.00 V and 5.00 A. (© 2024 Jos Verstraten) |
The functioning of the 'OUTPUT' pushbutton
If you use the 'OUTPUT' pushbutton to put the I8305 into standby mode, the voltage on the output buses should quickly go to zero. Pressing 'OUTPUT' again afterwards should cause the voltage to return to the set value just as neatly. No under- or overshoots should occur. We test this at a voltage of 15.00 V and a load current of 3 A. The results are summarised in the oscillogram below. The power supply behaves nicely!
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| The functioning of the 'OUT' pushbutton. (© 2024 Jos Verstraten) |
Behaviour in the event of a short circuit
We set the power supply to a voltage of 12.0 V and loaded it with 1 A. We then briefly short-circuited the device with a pushbutton. The behaviour of the output voltage is shown in the oscillogram below. There is no sign of overshoots, oscillations or other undesirable phenomena. Again, the I8305 behaves perfectly!
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| The behaviour in the event of a short circuit. (© 2024 Jos Verstraten) |
Influence of load variation on the output voltage
When you power a circuit, it draws a certain current. If this current suddenly increases or decreases, for instance when a relay switches on and off, it is important that the output voltage of the power supply remains constant and does not show any strange transient phenomena. We test this by setting the I8305 to 12.0 V and 5.0 A and supplying a load consuming about 1.0 A. Afterwards, we suddenly switch an additional load in parallel for a moment, so that the load current increases to about 4.5 A. You can see the reaction of the output voltage of the I8305 in the oscillogram below. Of course, the ripple increases slightly, but there is no sign of any unwanted transient phenomena. Again, excellent behaviour from this power supply!
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| Influence of load variation on the output voltage. (© 2024 Jos Verstraten) |
Functioning of the 'OCP'
This function works pretty well, the I8305 switches to standby if you draw more current than set. However, we noticed that when there was a short circuit, there were some pretty hefty sparks at the contacts. We therefore tested the short-circuit current by setting the power supply to an 'OCP' current of 1 A and maximum voltage. Afterwards, we shorted the power supply across a wire-wound resistor of 1 Ω.
In the oscillogram below, you can see the peak voltage generated during the short-circuit across this resistor. Curiously, after this peak, a voltage of about 1 V remains across the resistor for about one second before the voltage really goes to zero. So the 'OCP' function apparently works with a delay.
The sensitivity of the oscilloscope is 2 V/div and the peak is 3.5 divisions high. A voltage of about 7.0 V is thus generated across the 1 Ω resistor. This corresponds, according to ohm's law, to a short-circuit current of about 7 A! Apparently, the 'OCP' function discharges a large electrolytic capacitor across the output terminals.
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| The operation of the 'OCP' function. (© 2024 Jos Verstraten) |
Our opinion on the BSIDE I8305
There is little to criticise about this power supply. The measured performance matches the manufacturer's stated specifications nicely. We think the I8305 is an excellent power supply for the electronics hobbyist. Admittedly, we are not charmed by the way this power supply has to be set up. We prefer the old-fashioned rotary knobs rather than fiddling with small cursor keys. We also find the display far too busy. But this is obviously a very personal opinion and probably has a lot to do with our age and the way we were introduced to electronics 50 years ago.
However, it is clear that the I8305 is not very different from the dozens of almost identical lab power supplies marketed by just as many Chinese manufacturers. Another fact to take into account is that there are cheaper power supplies on sale that can also deliver 30 V at 5 A, such as one from Nice-Power that costs only about € 40.00 and can be controlled with four simple rotary knobs. Admittedly, such models do not have adjustable 'OVP' and 'OCP' functions and presets, but the question is whether you will miss that very much.
BSIDE I8305 Adjustable Power Supply
