Short Review of UNI-T UT136C

Today I will doing a short review of the UNI-T UT136C auto ranging multimeter. I got this for 20.95 USD from ebay which also converts to 28.32 SGD in today’s rate, which is bargain for an auto ranging multimeter. Shipping was free, and I got it in just 10 days, which is fast compared to the usual 3 weeks for shipping from China to Singapore.

Multimeter With Accessories

It arrived in box, without the retail packaging, indicating this unit must be factory direct. It came with a set of probes, a Chinese manual and a K-type thermocouple. The multimeter was wrapped in a bubble wrap, not the best one, but it came in one piece so it’s ok. For the manual, a Chinese version was included but there is an English version available on UNI-T’s English website as a pdf download. The probes were okay, a little bit thicker than the ones I used in my previous crappy $20 multimeter that had malfunctioned. There is no strain relief at all on the plastic ends of the probes. For that price and a great build quality you can’t really complain that much.

The build quality of the plastic probes feels solid, and its much thicker then the previous ones that I had used. The wires are also quite flexible. However, I would recommend getting another better set of probes. For the main multimeter itself, it is surrounded by what I would call soft touch plastic. Its red in colour, really nice to hold and has an ergonomic design due to its small size. It feels heavy and has a solid build construction. It has a flip out stand that is held in place by friction.

The LCD screen has 4 digits, enough for hobbyist use, which is what I intend to use it for. There is no backlight or single-led backlight so the LCD screen is a might be a bit hard to see under bright light but under normal room lighting it looks ok. Its size is approximately 5cm by 2cm.

There is an auto off option, where it will turn off after 10 minutes, a nice feature if you always forget to turn the multimeter off. It will sound a beep at the 9th minute to indicate to the user. There is an option to turn off this feature by holding down the select button when turning on the multimeter. The buttons are plastic, so none of those cheapy crappy membrane buttons.

The K-type thermocouple provided is not really of a good quality. It can only be used in temperatures of up to 230° C. The multimeter can measure up to the nearest degree. It measured 32 degrees C on ambient temperature in an air conditioned room, but I think it is off by 2-5 degrees, so I would only use this as a reference. As the manual indicates, it has an accuracy of ± 2.5%

The continuity measurements are not latched, but its fairly quick. It is sometimes intermittent even though both probes are literally touching together with me applying some force, but I think this is due to the probes themselves. I recommend users that use this feature a lot to get a better set of probes.

The autoranging feature is quite fast, although the autoranging in the resistance measurement can be slow. For me, I don’t really mind this as I use this measurement very rarely. As for the autoranging on the voltage measurement (which I use the most), it managed to get a stable reading within a second.

I particularly liked the 9V battery holder. The battery holder uses a removable holder which the battery sits into. So none of that fixed wire 9V connector.

As for the accuracy of the measurements of the multimeter, I’m not going to do it as I don’t have the proper equipment.

In conclusion, I would definitely recommend this multimeter to anybody who is starting hobbyist electronics. With its great build quality and price, its a good multimeter to start with.

Advertisements

Unbrick bricked FTDI chip

Last year around October, FTDI, the manufacturer of the popular USB to Serial converter used by many Arduinos released a driver (2.11.0 and 2.12.0) that bricks chips that it believes to be counterfeit. What it did was to set the PID (Product ID) to 0000 instead of 6001 which renders the chip unusable as Windows cannot find a driver for it. However, there seems to be a fix created by the maker community out there and so today we will be seeing on how to do it. I was given an Arduino Nano by my classmate but when I got it I could not program it. I then checked the PID at the device manager and it was showing 0000.

(This tutorial is largely based on Rei-labs.net tutorial here, but I decided to do my own version)

First thing to do is to uninstall the drivers. You can do this by going to device manager > Ports (COM & LPT) > FT232R USB UART. Right click and select Uninstall. Tick Delete the drivers software for this device and click OK.

Now go to C:\Windows\System32\DriverStore\FileRepository and delete anything that starts with FTDI (ftdibus and ftdiport)

FTDIBUSPORT

Now its time to install an older version of the FTDI drivers. Go to this website here and scroll all the way down. Download the 2.08.30 version of the drivers and depending on your computer’s OS, download the WIndows 8.1 if you have windows 8.1 or the Windows**** for all other versions.

DriverFolder

Extract the folders and double click on the exe file. Click next and accept all the license terms. Once done, restart your computer. Do not plug in your FTDI device yet.

Now go back to the  C:\Windows\System32\DriverStore\FileRepository folder and open ftdibus.inf. Open the ftdibus.inf file using any text editor. (Notepad will do)

First change the version of the driver. Find this line “DriverVer=07/12/2013,2.08.30” and change it to DriverVer=07/12/2023,12.08.30 ,without quotes. This is to fool Windows that this is the newest driver

Next go to [FTDIHw] and add this line just below it.

%USB\VID_0403&PID_0000.DeviceDesc%=FtdiBus.NT,USB\VID_0403&PID_0000

Next go to [FTDIHw.NTamd64] and add this line just below it.

%USB\VID_0403&PID_0000.DeviceDesc%=FtdiBus.NTamd64,USB\VID_0403&PID_0000

Next go to [Strings] and add this line below DriversDisk=”FTDI USB Drivers Disk”

USB\VID_0403&PID_0000.DeviceDesc=”USB Serial Port 0000″

Save the file to desktop and then move it back to the original folder that you opened it.

Now open ftdiport.inf. Basically we are doing the same thing as above, but slightly different

Find this line “DriverVer=07/12/2013,2.08.30” and change it to “DriverVer=07/12/2023,12.08.30” ,without quotes.

Go to [FtdiHw] and add this line just below [FtdiHw]

%VID_0403&PID_0000.DeviceDesc%=FtdiPort.NT,FTDIBUS\COMPORT&VID_0403&PID_0000

Now go to [FTDIHw.NTamd64] and add this line just below [FTDIHw.NTamd64]

%VID_0403&PID_0000.DeviceDesc%=FtdiPort.NTamd64,FTDIBUS\COMPORT&VID_0403&PID_0000

Now go to [Strings] and add this line just below PortsClassName = “Ports (COM & LPT)”

VID_0403&PID_0000.DeviceDesc=”USB Serial Port 0000″

Save the file to desktop and then move it back to the original folder that you opened it.

Although a restart is recommended, it seems to work for me without a restart. Now you can plug in your FTDI device and Windows will automatically install the drives. If not, go to device manager and click on Ports (COM& LPT) and right click “FT232R USB UART” and select update driver software. Select Browse my computer for driver software paste the line below as the location. Then click next. Windows should automatically find it and install it.

C:\Windows\System32\DriverStore\FileRepository

Once done, you should see “USB Serial Port 0000 (COMx). Your device can now be used, but the PID is still 0000. You can even try uploading a blink sketch if your FTDI device is an arduino . However, if you plug in your device to other computers, it will still not work. The next step is to change the PID back to default using FT_Prog

Download the software here or go to http://www.ftdichip.com/Support/Utilities.htm and scroll to FT_Prog and download the “Previous Version”

Once installed, launch the program and click on the magnifying glass. Then go to “USB Device Descriptor” on the left. Go to Custom VID/PID and select FTDI default. It should set the Vendor ID to 0403 and the Product ID to 6001. Or you can select Custom PID and set the Product ID to 6001.

FT_Prog6001FT_Prog6001default

Once done, click on the lightning icon. Double check that the Product ID is correct and then click on program. It should only take a few seconds. Then click close.

FT_Prog Program

Then unplug and plug in your device. Go to device manager and your device should not appear as USB Serial Port 0000. That means you’ve done everything correctly!

If you have any problems and/or questions, feel free to comment below 🙂

Tutorial : Replacing the Voltage Regulator on the Arduino

I was doing my school project and then suddenly the voltage regulator on my clone Arduino mega blew up. One of the 5V wires from the breadboard had accidentally touched a ground wire. Quickly, I removed my 12V power source. I then plugged in to the computer and luckily it was detected by the computer. This will be a tutorial on how to change the SMD voltage regulator on your Arduino. (Uno, Mega 2560 and etc). The Arduino I’m using is a clone Arduino Mega 2560. It is not really that hard as what you may think. It was previously using the 5V version of the AMS1117. The picture below shows the regulator after I had scrapped part of the plastic casing. It had ruptured to the point that I could simply use my tweezers to pick the plastic casing off. Burnt AMS1117 1. Using a side cutter/snipper, cut the 3 pins connecting the regulator to the Arduino PCB.

2. Use a soldering iron to heat up the tab of the voltage regulator. Depending on the wattage of your soldering iron, this may take a while. The Antex XS25 25W soldering iron I’m using did the job pretty quickly, only taking about 3 seconds to melt the solder around the tab.

3. Using tweezers, lift the voltage regulator up. Do this slowly, as you may rip the copper pads

4. Using a solder sucker or solder wick, remove extra solder on the pads and any remaining bits off the pads

5. Tin the pads with solder.

6. If you’re using a similar part to the one that burned, simply start soldering as per normal. Make sure that the pinouts are the same If not, go to step 8.

7. If you’re like me and only have LM7805 voltage regulator in the TO-220 form, and have a part that does not have the same pinout as the AMS1117, bend the ground and Vout pin so that they are crossing each other. Cover the pins with heatshrink or tape to prevent them from touching.

1         2         3                   1        3        2

|          |          |                    |         |         |

Vin     Gnd   Vout              Vin     Vout     Gnd

(Cross pin 2 and 3)

8. Solder them to the pads as per normal and you’re done. 9. Test by plugging a power source to the 2.1mm jack or the Vin pin. Use a multimeter to measure the 5V pin to make sure it outputs 5V. LM7805 Arduino

P.E.T : Personal Easy Transporter

P.E.T : Personal Easy Transporter

Project Supervisor: Teo Shin Jen (http://shin-ajaran.blogspot.sg)

The P.E.T is an open source personal urban transporter, designed to be used for commuting on sidewalks and for connecting the last mile between the MRT Train Station to home. It has a small size which makes it suitable being brought into MRT trains. The benefit of it is that: It is cheap, easy to build, highly adaptable to any spare parts the end user has, small footprint, and relatively acceptable travelling speed.

 

What its made of

It is made of a pair of repurposed car wiper motors from a previous project, bolted to a piece of 40 x 45 cm plywood. An Arduino Uno receiving commands from an app on an Android Smartphone through the HC-06 Bluetooth module is the brain of the whole transporter. It also gives commands to the Sabertooth Motor Controller through Serial UART. The app is readily available on the Google Play Store here. The P.E.T is powered by a rechargeable 24V LiFePO4/NiMH battery also recycled from a previous project.

How its made

The first thing to do is to test out everything first. The arduino is connected to a breadboard which has the HC-06 Bluetooth module and to the sabertooth motor driver with 24V powering the motor driver. Solder/Crimp fork and push on connectors for easy disconnecting/connecting of the motors. Remember to use sufficiently thick wires. The program for the arduino can be downloaded here.

Motor Driver Vin -> + 24V

Motor Driver Ground -> Arduino Ground and Power Supply/Battery Ground

Arduino Pin 1 -> Motor Driver S1

Arduino Pin 2 and 3 -> Bluetooth Tx and Rx to Arduino

5V and Ground -> Bluetooth Vcc and Ground

 

The second thing to do is to think of the layout, how everything is mounted to the plywood. Then measure the total size. I chose the wheels to be flush/’hidden’ within the plywood so as not to hit other surrounding things easily.

The third thing to do is to cut the plywood to size. I had it cut to 40 X 45 cm. Using an automatic jigsaw, it was cut from a larger piece of plywood. Then, draw guide lines for drilling the mounting holes. Before drilling, make sure that the mounting holes align with the markings. Double check! Using a hand drill, with a piece of scrap wood underneath, drill the holes needed. I used a 6mm drill bit as the bolts used are M6, giving it a tight fit. Next, using the appropriate screw size, screw in the motor to the plywood. As the screw head has a hexagonal shape, use a spanner to tighten it. Insert a nut to the other end, if available. The fourth step is to drill holes for the battery, Arduino and the Sabertooth motor driver. This should be fairly simple. Use self tapping screws for this as these screws do not go fully go through the wood. The last step is to fasten the battery to the plywood, connect the respective motors to the respective ports on the motor driver. Remember, one of the motors has to have its polarity reversed. Test the forward direction first to see which motor has to have its polarity reversed. If you don’t have the correct connector for the battery, use crocodile clips. Add a switch between the battery to the motor driver input. As the motor driver has a 5V out, use that to power the arduino through the Vin header. Refer to the earlier wiring diagram on top of this post. Solder wires to the Bluetooth module and a connector to the other end. Make sure the wires are all not hanging freely. Use wire fasteners to secure them.

And you’re done! Wasn’t that hard, was it? Now go out there and show the world what you have made!

TKKYIA 2015 Update #1

In the previous post, I talked about the Tan Kah Kee Young Inventor’s Award (TKKYIA). In this post, I will be talking about what are my detailed plans for the personal transporter.

The motors are from a car windshield wiper which was also used previously on another personal transporter. It has a gearbox to give it some torque while sacrificing speed, which is not really what is needed. Its fairly heavy, so this will ensure stability.

Testing the motor

A motor driver will be used to drive those motors using PWM. The PWM speed is regulated by the motor shield which receives serial commands via a Rx line from the arduino. This particular model is the Sabertooth 2X25. It can drive up to 25A per channel, but we only need about 800mA – 1.5A, so at normal operation, the currents are way lower than its limit.

Testing the HC-06 Bluetooth Module

Right now I’m just testing different android apps that send char characters to the bluetooth module and using the serial monitor to see the output. Originally I wanted it to be accelerometer controlled, but the app I found doesn’t really work on newer versions of android. There was another app of which I can customise every slider and button on the phone side. However, it is a paid app so in free mode I could only use it for 10 secs. The link to app can be accessed here.

The other apps only send a ‘f’ for forward, ‘b’ for backward and so on. There are predefined in the app so in the arduino sketch I have to match those commands. They also support moving forward while turning slightly. (8 directions of movement). Most likely I will use this method.

Main Things

The wood panel used is plywood and I had it cut to 40cm X 45cm. I gave some extra tolerance so that I don’t have to recut in case everything doesn’t fit. I can cut the wood to the smallest possible size later on.

The battery is rather large, so I have to see how it fits into the transporter. I have not gotten it yet, so I did not drill holes for the motor mounts. Currently I have 2 possible layouts as shown below, if the battery is really large, I would have to place it in between the motors.

20141230_153115

Mounting the Motors

The motors have a M8 standard holes, so what I’ll do is screw them in from the top of the wood panel.