Test/review of Electronic load DTU-CC01

HKJ · 2018-09-02T17:10:07.000Z

Electronic load DTU-CC01

Official specifications:

Material: PCB
Display: 128 * 64
Input Voltage: 3.6V~30V
Input Current: 0.2~3A
Voltage Resolution: 0.001V
Current Resolution: 0.001A
Rated Power: 25W
Max. Power: 35W
Wire Resistance Measurement: Pressure-drop method
Input Interface: USB-A, TYPE-C, Micro USB
Capacity: 0~9999.9AH, 0~9999.9Wh
Protocol Trigger: for QC2.0, QC3.0, FCP, SCP, AFC
Working Temperature: 0~70°C
Item Size: Approx. 11.5 * 4cm / 4.53 * 1.57in
Item Weight: Approx. 57g / 2.01oz

I bought from Aliexpress dealer: Sun-Shine Home

Like many devices from China this arrives in a envelope or in this case two envelops inside each other.

It included the load an a instruction sheet.

From left to right: The two current adjust potentiometers and the button, heat sink with fan, display and 3 different usb connectors.

The bottom is an aluminium plate, but it is not used as heat sink and the screws make it a bit hard on a table (Adding some rubber feet would be a good idea).

Display

There is many different screens on the display, I do not show all of them here.

Usual a fast click on the switch will change screen or line and long click will active current line (Activate trigger, function or change value). The user interface is fairly easy to use for a one button interface.

The main screen with actual voltage, current and power. It also shows actual temperature and maximum power and temperature.

Click for next screen or hold down to change maximums.

The load got too hot and is cooling down, it cannot turn completely off.

This screen is used for working with fast charge triggers.

Click for next screen or hold down for a list of fast charge schemes.

Here I have used the list of schemes to select and activate a fast charge scheme.

On the list of fast charge schemes one of the points is an automatic test for supported schemes.

This test is not 100% reliable, a charger that supports QC3 will always support QC2 and in the test above I did select QC2 on this charger.

Depending on scheme there is different options to activate them.

Load do not confirm if activating a scheme failed or succeeded, this must be seen on the voltage.

Next screen is accumulated energy and capacity, hold button down to reset.

A cable test, this requires a stable USB power supply. First plug the load into the power supply, select a current level and hold down the button to record the reference. Next use the cable between the load and the supply (Do not touch the potentiometers) and it will show the cable and connection resistance.

Load testing

Minimum stabilized current is about 0.4A, at lower current there will be a peak just below 5V
Maximum current is about 3.2A
It is fairly easy to adjust current to two decimal places, the 3. requires more care.
Load have power and temperature overload protection.
The load has USB-A, micro usb and USB-C connectors, all in parallel.
USB-C connector includes resistor to turn usb-c output on.
USB load can trigger many normal usb fast charge schemes, but not USB-C PD.
Fan is always on when load is powered.
Display can be rotated, i.e. for view from connectors or from potentiometers.
Current change during 60 minutes with 3A load at 9V is 0.033A, i.e. 1.1%
Fine adjust is about 250mA range

Some of the current curves looks a bit strange. The first point is that the load may handle 30V, but it only works below 18V, this is perfectly fine for most USB testing. The next point is the build-in protection, when the load gets too hot it turns it off for some time and then on again, this is especially obvious on the yellow curve, what is a bit strange is that sometimes it only turns off for a short time, other times for considerable longer time.

A closer look at the low current curves shows that the load is not good at this, there is a current spike just below 5V, it means for testing below 5V the minimum load current is about 0.4A, at 5V and higher it can go lower.

The load is rated for a maximum of 35W with a constant load of 25W, here I applied slightly below 35W and in about 1½ minute the load got to hot and took a break while cooling a bit down, the it engaged again. This continues in a cycle.

Reducing the load to 25W (Even a little bit above) with a 9V 3A test worked better, here the load could keep the temperature down. The display shows about 63°C (Ambient is about 25°C) and the overload is at 70°C.

M1: 52.2°C, M2: 49.2°C, HS1: 62.9°C
HS1 is on the circuit board next to the heatsink and that temperature matches the display fairly well.

M1: 64.5°C, HS1: 80.3°C

HS1: 89.4°C
The transistor is warmer (it is probably rated for 150°C inside).

A look at the circuit

The load has a processor (ARM MM32F031 K6T6) that directly controls the display (There must be a controller in the display). There is an external EEPROM (U7: K24C08) for parameter storage. The internal power supply is fairly advanced with two switchers, one for the fan (U4: marked AL723) that uses a inductor and diode (d1) and one for the electronic (MC34063A) also using a inductor and diode (D3) and two linear regulators (U8: SE8550 & U2: SE8533).
The current sense resistor is two resistor in parallel (R8 & R10: 2x0.2ohm) with a OpAmp to amplify the signal (U1: marked CD53) and another (U5: marked CD53)to control the power mosfet (IRFZ44N).

Conclusion

The load works fine for testing usb power supplies, but the fast charge identification is not 100% reliable and it do not work up to the rated voltage of 30V or the maximum QC usb voltage of 20V (The trigger support 20V).

Even with these issues I will call it a fairly good load for usb, except USB-C PD that it do not support.

ActiveAl · 2018-09-02T22:47:59.000Z

HKJ, As a flashlight enthusiast, I love to measure things. But why would I buy this tester? Thanks.

BlueSwordM · 2018-09-02T23:17:11.000Z

Well, to test out USB powered devices!

Electronic loads in general are extremely useful.

In case of USB loads, they can be used to test cable resistance by measuring voltage drop over a set current, which can help weed out low quality USB cables, and in the case of very bad ones, get a refund. Which did happen for me once :person_facepalming:

You can also test the efficiency of a powerbank at a set current, which is good, or even better, test its efficiency and output power to see if its specs are true, or are fakesium.

In relation to this, you can see the total power output of a USB power supply/powerbank to see how much power its ports can handle outputting, if the ports themselves are rated truthfully, and see if it’s actually unsafe to use it if it gets dangerously hot.

Finally, you can use it as a mini heater

ActiveAl · 2018-09-02T23:46:16.000Z

OK. let me see if I have this right. You plug this device's USB type A connector into a USB power supply, select the amps the tester will draw, and then read the actual voltage and current output in the LCD display? Is this how it works?

What are the two terminals opposite the USB Type A connector for? Thanks.

BlueSwordM · 2018-09-03T00:03:58.000Z

1. Yes that is it. Select the amp draw, and then read the voltage and current output the USB power supply actually outputs. At say 2A, good ones will stay at 5V/2A, while bad ones will collapse to say 4,5V/2A, which is outside of the allowed USB voltage range.

2. These are two potentiometers, one from current draw, the other is at what voltage the load draws. The 1st one is what all USB electronic loads can do, while the other one is used when you trigger a special protocol like QC 3.0 or Apple 2.4A. Since they use a variable voltage, you can change the voltage of their outputs too so you can see how they behave.

If you want one similar to this but quite a bit better, check these out:
https://www.aliexpress.com/item/RD-HD25-HD35-Trigger-QC2-0-QC3-0-Electronic-USB-Load-resistor-Discharge-battery-test-adjustable/32917594486.html?spm=2114.12010608.0.0.1f535bc526HGcQ

I would just buy one IMO. RD Tech makes some dope power supplies and meters. In this case, since there is still a discount, I would just pick the HD35. From what RD Tech said to me and what I’ve read, the HD35 is slightly better in terms of components specifications, and uses a quieter more efficient fan since it has hydraulic bearings. Both can also trigger most USB fast charging protocols, except for Dash/VOOC charge and Huawei’s Super Charge.

ActiveAl · 2018-09-03T01:18:26.000Z

OK just ordered the HD35 from the RD Official store on Ali, and downloaded the manual. The HD35 is cheap enough to just order and play with. Also found this thread on the HD25/35. Thanks!

BlueSwordM · 2018-09-03T01:22:26.000Z

I ordered it too. Was too tempted to take it, especially since it was better and cheaper than the LD25 a few days ago

angerdan · 2018-09-04T19:17:47.000Z

Thanks for the review!

FlashPilot · 2018-09-04T23:32:34.000Z

Thank you for your typical, super-detailed, awesome review! :+1:
Its nice to see the appearance of so many useful and accurate multi-function budget USB load and test devices coming to market recently. What similar gadgets do you have planned for review in the near future?

HKJ · 2018-09-05T06:07:45.000Z

FlashPilot:

What similar gadgets do you have planned for review in the near future?

More loads and I have also looked a a few usb meters.