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Using Cheap Asian Electronic Modules By Jim Rowe USB-PD Triggers, Decoys & Testers Left-to-right: the FNC88, WITRN UPD005, ZY12PDN-1 & XY-WPDT Following on from the article last month on USB-PD charging modules, we shall now examine some of the many low-cost PD trigger/decoy and tester modules that have appeared recently. These allow you to take full advantage of the USB-PD chargers’ capabilities and use them as versatile and efficient power supplies. A PD trigger is an interface circuit that can manage the negotiating protocols necessary to request the required voltage and current levels from a USB-PD supply, as described last month. As soon as it is connected to a USB-PD compatible host, it engages with the host via the CC1 or CC2 channels to achieve the voltage and current levels that are needed – assuming these are available. Some of these modules are also known as “decoy” or “poll detectors”. These terms all seem to mean much the same thing as PD trigger. Another variant combines the functions of a trigger/decoy module with those of a USB-PD digital meter, so it can display the available or selected voltage(s) and current(s). We’ll start by looking at the smallest, simplest and cheapest of the trigger modules. ZY12PDN-3 “naked” PD trigger The ZY12PDN-3 module is tiny, as you can see from the photos. Everything is mounted on a PCB measuring just 30 x 15mm, with the USB-C input socket at one end and a small two-way screw terminal block at the other end as the power output. The ZY12PDN trigger module is 88  Silicon Chip available in three versions, which differ only in their output connector or lack thereof. Instead of the screw terminal block of the ZY12PDN-3, the ZY12PDN-2 has a USB Type-A socket, while the ZY12PDN-1 has no output connector at all. The trigger circuitry on the PCB uses two main chips: an STM32F030F4P6 microcontroller and a PBAFH device, which is likely the USB physical layer interface. There’s also a small pushbutton switch that can be used to select the voltage and power level required from the USB-C PD host, and an RGB LED to indicate the selected voltage/ power level. When the ZY12PDN is first connected to the PD host, the LED glows red to indicate the default 5V supply voltage. If you then press the button, it will attempt to select a 9V supply. If the PD host has this voltage available, it will switch its output to 9V, and the LED will change to yellow. If you press the pushbutton again, this will attempt to change the supply voltage to 12V. If the PD host has this voltage available, it will switch its The ZY12PDN-3 PD trigger, shown enlarged for clarity. There are two other versions of this module with either a USB Type-A socket or no connector fitted instead of the screw terminal block. Australia’s electronics magazine siliconchip.com.au The WITRN UPD005 is an alternative to the ZY12PDN module. output to 12V, and the LED will change to green. Further button presses will change the voltage to 15V (light blue), then 20V (dark blue) - assuming the host can supply these voltages. If the host doesn’t have one of the voltages you request, the LED will glow purple, and the voltage will stay at the highest voltage which is available. There’s also a ‘demo’ mode, where the LED glows white and the supply voltage cycles through the available levels at approximately 1Hz. If you plug the ZY12PDN into a host port that does not support USB-PD voltage and power negotiation, after about four seconds, the LED will flash blue to warn you that there is no USB-PD support. However, it will still pass through the normal 5V VBUS power. So the ZY12PDN trigger module essentially provides the ability to manually select the voltage from a USB-PD power source. And it does this for a cost of around $11-13, depending on how many you order and from which internet supplier. So it’s a bit limited in terms of the voltages you can request and has no provision for taking advantage of PPS ‘fine tuning’. But if you just need the ability to manually select one of the main PD voltage levels, it is a good choice. For example, you could use it in combination with a computer or USB charger as a very basic bench supply to power something like a breadboard. There are other ‘naked’ trigger modules available that are very similar to the ZY12PDN. One example is the WITRN UPD005 V20, available from suppliers like Banggood for much the same price as the ZY12PDN. I obtained one of these and tried it out, and it did the job just as well as the ZY12PDN. FNC88 PD trigger module & meter The FNC88 PD trigger is slightly larger than the ZY12PDN, but not by much, especially considering that it also includes a digital meter. It measures just 40 x 25 x 10mm, not including the USB-C input plug. And it’s not exactly ‘naked’ either, with a shield PCB mounted 3mm below the main PCB and a protective plastic sheet above the 24mm diagonal colour LCD screen. It’s made by FNIRSI Technology in Shenzhen, China, and is available from quite a few internet suppliers, including Banggood, for around US$25 plus delivery. It comes in a protective case with a clear window, measuring 90 x 62 x 18mm. This should make it sturdy enough for portable use. The FNC88 PD unit has USB-PD bidirectional capability, and this also applies to the built-in digital meter. So PD triggering and measurements can be made using either the USB-C plug at one end or the USB-C socket at the other end as the power source, with the opposite end connected to the ‘sink’ device. This also means that the FNC88 can be connected between a USB-C cable and the USB-C connector of either a host or sink device. On one side of the FNC88’s main PCB, there’s a mini USB-C socket, which extends its capabilities to measuring the current drawn by devices with that type of USB connector. Then on the other (‘top’) side are three tiny pushbutton switches, and an equally small slider switch. The slider switch is to enable or disable the trigger’s USB-PD protocol communicating ability, while the three pushbuttons are used to select the functions of the digital meter. The specified supply voltage range of the FNC88 is 4-24V, and its current range extends from 0 to 5A, so it’s capable of dealing with all devices conforming to the current USB-PD specification. The voltage measurement resolution and accuracy are specified as 0.1mV and ±(0.5% + 2LSD), while the current measurement resolution and accuracy are specified as 0.1mA and ±(1% + 2LSD). Quite impressive! Other features of the FNC88 include measurement and display of: • The power being drawn by the sink device (0-150W, with a resolution of 10mW). • The charge delivered to a battery over a known charging time (0-99,999.9mAh with a resolution of 0.1mAh). • The energy delivered to a battery or other sink device over a known delivery time (0 - 9999.999Wh with a resolution of 1mWh). The front and rear view of the FNC88 module; you can just see the three function buttons at the bottom of the rear view, along with the switch that connects the built-in PD chip to the CC1 pin. siliconchip.com.au Australia’s electronics magazine August 2021  89 This side of the FNC88 module has a micro USB interface which is only used to flash the firmware. • The ability to record measurements over a period of 0-999 hours, 59 minutes and 59 seconds with a resolution of one second and an accuracy of 10 seconds/hour. The PD trigger section of the FNC88 supports these protocols: QC2.0, QC3.0, FCP, SCP, AFC and PD 3.0. Although the FNC88 does not come with any user operating manual, you can download one as a PDF file from the FNIRSI website at siliconchip.com. au/link/ab7n I gave the FNC88 a quick rundown, comparing its voltage and current readings with those from my Agilent U1251B DMM. This showed that the accuracy and resolution of the FNC88’s digital meter were within their claimed figures. So overall, the FNC88 seems to be a very capable and useful device. My only real complaint is that you need either good eyesight or a strong magnifying glass to read the display on its 24mm diagonal LCD screen. There are several other USB-C PD trigger/DM devices available from Banggood and other internet vendors. A good example is the Riden TC66, which is almost precisely the same size as the FNC88 and very similar in its functions and facilities. It’s available for much the same cost as the FNC88. I have seen a suggestion on the internet that the FNC88 might be a knock-off of the TC66, or vice versa. See siliconchip.com.au/link/ab7m The XY-WPDT trigger unit & meter Another USB-PD trigger/meter unit available from many internet suppliers, including Banggood, is the XY-WPDT. At the time of writing, Banggood was selling it as a kit for only $15 including delivery. It is made by the same firm in China which makes the XY-PDS100 ‘quick charger’ we looked at last month. Although the XY-WPDT comes as a kit, assembling it is not difficult and doesn’t involve any soldering – just the use of a very small Philips-head screwdriver, which is included in the kit. The PCB itself is already assembled, so all that remains is fitting the front and rear panels around it using the M2.5 screws and tapped spacers provided. When you complete the assembly, the XY-WPDT measures a modest 61 x 25 x 11mm (not including the USB-C plug protruding from its input end). It’s only a little larger than the FNC88. The main output is via a USB Type-A socket at the opposite end of the unit to the USB-C input plug, and the XY-WPDT comes with a 100mm-long output cable with a Type-A plug at one end and a 2.5mm inner diameter concentric power connector at the other. There are also a couple of USB-C sockets on the unit itself near the USB-C input plug, one on each side, arranged so that the XY-WPDT can measure the voltage and current passing between them. The specifications of the XY-WPDT are not all that different from that of the FNC88. It can negotiate an output voltage between 4V and 20V using either PD 2.0 or PD 3.0 protocols. It can adjust the voltage in either 1V, 100mV or 20mV increments or decrements if the PD host can respond to PPS negotiation (like the XY-PDS100). The meter function can measure the voltage with a rated resolution of 10mV and a precision of 0.3%, and current with a rated resolution of 1mA and a precision of 0.5%. Not quite as good as the FNC88, but still very useful. The readout of the XY-WPDT is a 4-digit 7-segment LED display with 9mm high digits, so although it is not The XY-WPDT is sold as a kit by Banggood, and only requires fitting the components together with a screwdriver to assemble it; no soldering is necessary. 90  Silicon Chip Australia’s electronics magazine siliconchip.com.au as fancy as that of the FNC88, it’s significantly easier to read. Function switching is done via two tiny pushbutton switches (K1 and K2), one on either side of the unit. There are also four indicator LEDs; three indicate the voltage steps in PPS mode (1V/100mV/20mV), with the remaining one indicating current measurement mode. Like the FNC88, the XY-WPDT does not come with any operating manual, nor could I find a manual on the internet. The only information on using it seemed to be in the XY-WPDT follow-up info on the Banggood website, which turned out to be rather terse and not easy to follow. I gave the XY-WPDT a quick checkout coupled to the XY-PDS100 PD charger, and the results were very close to the rated figures for resolution and precision of both voltage and current. Overall then, the XY-WPDT PD trigger/meter is quite a good performer, and very good value for money. My only real complaint is that the method it uses to select the voltage mode using the two tiny pushbuttons K1 and K2 is really tricky, with various short and long presses on each button making it not at all easy to set the XY-WPDT to a particular voltage level, especially in PPS mode. This seems to be because both buttons have different functions according to how long they’re pressed, so you can easily flip things into a different mode without meaning to. In theory, the combination of the XY-WPDT and the XY-PDS100 should make a digitally adjustable DC power supply with its output variable to any voltage between 4V and 20V, but this isn’t all that easy in practice. It would be a lot easier if the two tiny pushbuttons were increased in number, with a smaller number of functions per individual button and less dependence on the time they are pressed. But for applications where you want to ‘set and forget’, it works acceptably well and provides excellent value for SC money. Useful links USB-C: https://w.wiki/nto USB-PD: https://w.wiki/34dT siliconchip.com.au/link/ab7l siliconchip.com.au/link/ab7m Quick Charge: https://w.wiki/34dU siliconchip.com.au The XY-PDS100 quick charger (detailed last month) is shown connected to the XY-WPDT trigger unit, displaying the output voltage. Here’s what the assembled XY-WPDT module looks like. The two extra USB-C sockets on either side allow the unit to operate in pass-through mode. From left-to-right we have the USB-C input, PPS mode LEDs (1V, 100mV & 20mV steps), K1 switch, and current indicator LED. The USB-C input is used with the matching output connector on the opposite side to control and measure voltage or current. Pressing the K1 switch changes between displaying current or voltage, while holding K1 just turns the screen and indicator LED off. Switch K2 is used in conjunction with K1 to change the voltage setting, and is a bit more complicated to set, see: siliconchip.com.au/link/ab7o Australia’s electronics magazine August 2021  91