Notebook PC Power Adapter - Dell 90W

Many years ago, I wrote about my experience with the "smart" power adapter.  As I changed my work notebook computer from Dell to HP, despite of same power rating and same 3-pin barrel plug, the HP computer would not detect the Dell power adapter.  It seems such a waste not to have a common standard of power adapters.  (The move towards USB C PD for all mobile devices should make thing better.)  So I decide to crack one open to see what exactly the center pin does.  This is a 90-watt dell power adapter (19.5V 4.62A); it is not too hard to crack the case open.   The power adapter is made in China by Delta Electronics, a Taiwanese power product company.  The date code is "0731". The three wires go connections labelled VO, GND and DATA on the single layer PCB.  The DATA trace is connected to a 3-pin TO-92 device, with marking "75M518E BYE TI".  No information is found on this device, so it is likely a proprietary device.  The DATA signal has an 130-Ohm resistor in series and is clamped by a Zener.   The device is powered directly off the 19.5V.

The primary is switched by Infineon SPA15N65C3 650V 0.28-Ohm N-channel MOSFET.  The secondary side is Vishay Siliconix SUP60N10 100V 0.02-Ohm N-channel MOSFET.  The controller has the marking "DAP6A",  which seems to be a custom specific device from ON Semi with the part no. DAP006, PWM Current−Mode Controller for Free Running Quasi−Resonant Operation and is equivalent to NCP1200.  On the secondary side, there is an 8-pin IC with marking, "DAS001 ST", which appears to be equivalent to TSM103W, a dual opamp with 2.5V voltage reference.

When the power connector is plugged into the computer, the center pin is pulled up to about 3.3V.  Then there is data activities on the line.  If the center pin is not connected to the power adapter, the center pin from the computer toggles every 3 seconds with 2 seconds high.

When the center pin is not connected, the power draw drops to 20W and the computer runs at a slow clock rate (about 800MHz).

Aukey DR01 Dash Cam

It features SonyIMX323 with 1936 (H) × 1097 (V) active pixels, with pixel size of 2.8um, Novatek NT96655 with 128MB DDR3 SRAM and 2x 2.7V 3.3F super cap.  It produces reasonable good quality video for most lighting conditions.

Recently, it kept resetting the time.  And the dash cam does not record until the date/time is set.  It is suspected that the time keeping battery is faulty.  The coin battery appears to be FDR rechargeable lithium battery, ML621, 5.8mAh, 3.3V, 6.8x2.1 mm.  The number of charge/discharge cycles are rated for 300 at 23C.   The voltage at the end of capacity is about 2V and 2.5V at the half capacity.  The standard charging method is constant voltage of 3V with 1KOhm.

The battery voltage is measured at 2.8V.  Interestingly, the dash cam started working fine after it was opened and continued to work after it was put back.  Perhaps something was shorting the battery?

Tek Scope Screen Capture

I've been taking scope pictures with my phone, but sometimes the pictures do not have good focus and the picture size is large.    The Tek scope has a serial port which commands and data can be sent and received.  But I have had a lot trouble to get the Tek's own software to work.   For screen capture, it is actually a lot simpler: just set up the hardcopy to output to RS232 and choose a format such as PNG, then just hit the hardcopy button, the data come out on the serial port.  Now it is just a matter of capturing it on the PC, which can be a simple Python script using pyserial.   A null modem cable is necessary; the maximum baud rate is 38400.  It takes about 3-4 seconds to get the screen shot, which is much better than you can capture with your phone.

USB Hub

This is a 7-port USB hub with 4 USB3 ports and 3 USB2 ports by Zoweetek, ZW-H355.  It essentially is consisted of two ICs, GL3523 by Genesys Logic is a 4-port USB3.1 compliant hub controller and HS8836 which appears to be a 4-port USB hub controller but very little information is available online.   It appears that one of the USB2 signals goes from  GL3523 to HS8836 and HS8836 has 4 pairs of USB2.0 signals going to 3 USB2 ports and one of the USB3 ports.  The PC board is not well cleaned especially around through-hole connections, perhaps the switches and connectors are hand soldered.  It is not clear if the high-speed traces are matched.  There is a footprint for input USB3 connector, but here the wires are directly soldered to the board.

RaspberryPi Zero W

I came across a RaspberryPi Zero W, the older generation RPi Zero with WiFi.  For $10, it is a great little board.  Although it can run the desktop environment, it cannot really be expected to run the memory intensive applications such as internet browser because of limited memory.  But 512MB is a huge amount of memory for embedded systems.  To run the camera, it needs to allocate 128MB to the GPU (perhaps 64MB if only still picture).

It is straightforward to wiring up a display module (2.7" 128x64 OLED).  And with the python module luma.oled, the display is up and running quickly.

Starter Motor

I recently had to replace a starter motor, so I got a chance to look the interior of the starter motor assembly.    The starter motor assembly is consisted of a DC brushed motor, a solenoid and gears.   

The DC motor has series field winding: the input positive battery coming through the solenoid switch first goes into the field winding, then to a pair of copper brushes.  The negative terminal is the chassis connecting to the other brushes.  

The solenoid serves two functions: switching the battery power to the motor and pushing the gear to engage the engine flywheel.  Because of the large starting current (hundreds of amperes),  heavy gauge wires and large copper contact are used.   The solenoid has two coils: push-in coil that is connected to the motor positive terminal (the output of the switch) and the holding coil connected to the chassis.   This is a clever design: before the motor power switch is closed, the push-in coil is energized through the motor windings.  Once the motor power switch is closed; the push-in coil becomes inactive and a lower power holding coil keeps the solenoid in place.

The motor shaft is geared to the output the starter.  The solenoid has a spring loaded pin that pushes the gear to engage the flywheel.  There is also a clutch that prevents the flywheel to backdrive the motor once the engine has started.

Thermostat

The check engine light came on and the code from the ODB port is P0128, which usually means the thermostat stuck open.  This is corroborated by the temperature indicator which does not rise quickly and stays below normal.  This is an emission related issue because the fuel does not burn completely in sub-normal temperature and more pollutants are released and the gas mileage is reduced.

After draining the coolant and removed the thermostat, the thermostat does not appear open.  A new thermostat is installed; the temperature indicator behavior is noticeably different: the initial temperature rises quickly and is  regulated to just below midscale.  Checking the thermostat operation by placing it in hot water, it opens as expected and closes as the water cools.  Why is it stuck open?  Close examination finds that the valve is not closed tightly; it is a little crooked, perhaps warped after many years of operation.  But it is still fairly remarkable that the thermostat is a simple robust mechanical design.  It is based on thermal expansion of material at relatively accurate temperature of 82C; it is submerged in hot liquid, no electronics involved, no energy needed.  Sometimes simple mechanical device is a better solution than electronic control.