Karl Johnson, Author at CNX Software - Embedded Systems News

September 5, 2019July 8, 2020 by Karl Johnson - 57 Comments

How to Easily Calibrate Retraction in 3D Printers

[Update July 2020: It is now recommended to use Calibration Generator program instead of the Google Doc Spreadsheet in this article] Hey, Karl here with a short article on retraction tuning. I really enjoy reviewing 3D printers and all things 3D printing with one exception…. when I have to calibrate retraction (aka retraction tuning). It takes so much time. What is Retraction? While 3D printing on a standard FDM printer, the filament is pushed with an extruder motor that has a gear attached. It pushes the filament, either directly into the hotend assembly or through a Bowden tube to the hotend. Molten plastic is then layered to produce a model. When it is printing nearly all prints require non-extruding movements. During the extruding moves pressure builds up and in order to stop stringing and blobbing during non-printing moves, a retraction happens. There are 2 main variables that affect this: the […]

August 26, 2019 by Karl Johnson - 10 Comments

Beelink GT-King (Amlogic S922X) TV Box Review

Rant Karl here. I have been playing around with Android boxes for several years. Unfortunately, some fundamental issues from when I first started playing around with these boxes are still there. They have come a long way since the MK808 with Rockchip RK3066 processor. The MK808 was my first endeavor into Android on the TV in 2013. I can’t believe it’s been nearly 6 years. In 2014 Google introduced Android TV and the Nexus Player. It was designed for a TV and controller. The first boxes/sticks adapted the stock Android experience to run on a TV, but without a touch interface the experience was/is not optimal. Sure you get thousands and thousands of apps but a lot of them don’t work. Unfortunately, this hasn’t changed much. If these boxes came with Linux and Android I don’t think I would complain as much. I would consider it a tinkering box. But […]

June 18, 2019 by Karl Johnson - 11 Comments

Review of SainSmart Genmitsu CNC Router 3018-MX3

Hey Karl here. Back in September of 2018 I reviewed the Sainsmart Genmitsu 3018 Pro. Sainsmart has now further upgraded the 3018 and asked for a review of it. Let’s take a look at the changes and the evolution of the 3018 and see if the increase in price is worth it. You can find the original 3018 on sale for about $200. The pro version can be found for about $250, and the CNC Router 3018-MX3 for $350. I won’t go into too much detail like I did in the previous review. I suggest reading the pro version after reading this one. Most of the experiences and solutions apply to this version. Build Building the CNC Router 3018-MX3 was a breeze. The instructions are fantastic. I struggled a little bit to read the small booklet that came with the kit and afterwards I found a PDF on the Sainsmart […]

June 2, 2019June 3, 2019 by Karl Johnson - 17 Comments

Review of Zonestar Z6 Low-cost 3D Printer

Ugh…I don’t like calling these reviews. I like to say that I am sharing my experiences with the products. I have a fair bit of experience under my belt using 3D printers now but still don’t consider myself an “expert”. I think that I have had about a dozen come through here. Anyway on with the show. Today we are going to look at a very economical 3D printer: the Zonestar Z6. I have to say I wasn’t expecting much. I read/ watch a lot of reviews about 3D printers and sub $100 printers aren’t typically very good. Gearbest recently had the Zonestar Z6 on sale for $99 that Jean-Luc recently posted here on CNX Software but is currently $120. Let’s see how it prints. Some assembly required I designed a spool holder but not very good. The whole printer rocks when the full spool is on it. The tiny […]

April 4, 2019 by Karl Johnson - 6 Comments

SainSmart DS213 Review – A Portable Mini Digital Storage Oscilloscope

Hey Karl here with another oscilloscope review. We are going to look at the DSO213 (aka DS213 mini DSO). It is a new handheld oscilloscope in the DSO line. I recently reviewed an oscilloscope that was a tethered USB oscilloscope and will use it as a comparison. The DSO213 is a compact, battery powered, oscilloscope that increases some specs over previous version the DSO203. DS213 Oscilloscope Unboxing and Teardown Pictures . I thought this was an interesting design choice. Pogo type pins connect this board. This series of scopes has been reviewed quite a bit and they have been well received and for a hobbyist they seem to be adequate. Model DSO213 DSO203 MCU STM32F103VE STM32F103VE ADC HWD9288 AD9288 Channels 2 analog, 2 digital 2 analog, 2 digital Analog Bandwidth 15MHz 8MHz Max Sample Rate 100MSa/s 72MSa/s Maximum Memory Depth 4K 4K Horizontal Sensitivity 100nS/Div~1S/Div(1-2-5sequence step) 0.1uS/Div~1S/Div(1-2-5sequence step) Vertical Sensitivity […]

January 26, 2019 by Karl Johnson - 11 Comments

SainSmart DS802 Review – A Dual Channel Virtual PC Oscilloscope

Hey Karl here. Today we’re going to look at the SainSmart DS802 Dual-channel oscilloscope. I have always wanted to have an oscilloscope and add it to my tools. When SainSmart asked to review the DS802, I was pretty excited. I can get my nerd on and troubleshoot all kinds of things. A couple weeks later it arrives and my anxiety kicks in. How the heck do I review an oscilloscope. I used an oscilloscope in high school in a class called principles of technology. But we never really went into much depth and only looked at the signals generated by a signal generator. I understand the basics. This is written from a perspective of a complete noob. SainSmart DS802 Specs Pulled directly from Sainsmarts website: Channels: 2 Analog channels Interface: USB 2.0 Output: 1k HZ amplitude 1.5V, 50% duty cycle square wave signal Maximum sampling rate: 80 MSps per channel […]

January 10, 2019April 13, 2021 by Karl Johnson - 29 Comments

Radxa Rock Pi 4 Review – Part 1: A First Look at RockPi 4B Performance Set

Hey, Karl here with another RK3399 board. This one is by Radxa and is called the Rock Pi 4. There are 2 main variants to this board and I was shipped the B version “performance set” which includes a power supply, heatsink, and acrylic case. Also shipped was 16gb eMMC 5.1 module, eMMC flashing board, and USB-TTL debug cable. It looks like the difference is the B version has AC wifi and GbE LAN with PoE support with a hat. The A version only has GbE. Rock Pi 4B Performance Set Unboxing Some of the more notable specs eMMC module support M.2 NVME SSD support (SATA not supported) HDMI 2.0 4k@60htz MIPI DSI 2 lanes via FPC connector 3.5mm audio jack MIPI CSI 2 lanes via FPC connector, support up to 8MP camera 802.11 ac wifi Bluetooth 5.0 40-pin expansion header : 1 x UART 2x SPI bus 2x I2C […]

December 28, 2018April 13, 2021 by Karl Johnson - 7 Comments

Khadas Edge Review – Part 3: Android 7.0 Preview

Hey Karl here with a look at a preview of Android on the Khadas edge. Jean-luc has done 2 parts already. The first one looking at the hardware side, and a second looking at Ubuntu. A third img is available that for LibreELEC. The initial release was very barebones, and the 2nd version is much more polished with the Play Store installed now and overall feels snappier. Khadas is supposed to be sending an Edge over to Super Celeron, and I hope they follow through. DHL DHL really messed up my board. Here are some pics. I will only be testing with Ethernet because the WiFi antenna got damaged badly and even bent the heatsink. I think the board is slightly damaged as well. I can only flash using the buttons on the board and not the carrier board. Everything else seems OK. Due to the damage, I am using […]