A heat shield for the Atten 858D hot air rework station

The Atten 858D Hot Air Rework Station is a very handy tool. Until now I have only used it for removing some SMT components and for heat shrink tubing. Check the EEVblog for an in depth review of the Atten 858D.

Like any cheap Chinese gear, you should open it before turning it on to make sure it is electrically safe. My unit did have a grounded heat element, but the case was not grounded. This was easily remedied by sanding down the paint on the inside of the case around the mounting holes of the transformer and then making an additional connection between the ground pin of the mains input and one of the mounting screws of the transformer. A quick continuity check confirmed this hack was a success.

This Atten hot air rework station has a very nice feature: when you put the element in the stand, the heating element turns off and the nozzle keeps blowing until the temperature drops below 100°C. Although I regularly knocked the handset down because my rework station was on the front of my desk, I hesitated to put it more in the back. The backdrop of my workspace is a wooden panel and it would not withstand the initial heat escaping from the rework station… Continue reading A heat shield for the Atten 858D hot air rework station

Arduino OpenWRT USB connection

This central heating monitoring system I am working on is built around an Arduino Uno. I want to hook it up to a Asus WL-500g deluxe router running OpenWRT. I found that this router has an internal header with two serial ports and I was planning to use one of these ports to link to my Arduino.

Pondering how I was going to do the logic level shifting from the 3.3V on the Asus to the 5V on the Arduino, I wondered if it would be easier just hooking up the Arduino via one of the two USB ports on the Asus WL-500g deluxe router. Plugging in the Arduino via USB did not look very promising, a dmesg only showed:

usb 2-1: new full speed USB device using uhci_hcd and address 2

Plugging in the Arduino on my Ubuntu Linux desktop showed that the Arduino is a “USB ACM” device:

[25009.512051] usb 3-3: new full speed USB device using ohci_hcd and address 4
[25009.731110] cdc_acm 3-3:1.0: ttyACM0: USB ACM device

So, I needed some kind of ACM driver for OpenWRT. A quick search revealed that I needed the usb-acm kernel module, so that is what I installed:

root@OpenWrt:~# opkg update
root@OpenWrt:~# opkg list | grep -i acm
kmod-usb-acm - - Kernel support for USB ACM devices (modems/isdn controllers)
root@OpenWrt:~# opkg install kmod-usb-acm

Plugging in the Arduino now shows the right logs in dmesg:

usb 2-1: new full speed USB device using uhci_hcd and address 3
usb 2-1: configuration #1 chosen from 1 choice
cdc_acm 2-1:1.0: ttyACM0: USB ACM device

So we can now use /dev/ttyACM0 to talk to the Arduino. Ciao, mondo!

root@OpenWrt:~# ls -l /dev/ttyACM0
crw-rw-rw-    1 root     root     166,   0 Oct 25 23:36 /dev/ttyACM0

Capacitor replacement

I had opened my Asus WL-500g deluxe router because I was planning to hook something to the internal serial port header. I immediately spotted a dodgy looking capacitor.bad capacitor

This 6V 1000µF capacitor had a bulging top and after desoldering only measured 5µF! I replaced it with a 16V 1000µF capacitor:

new capacitor

The area around the capacitor is getting pretty hot, that is why I plan on adding a fan later.