Making Ruideng DPH5005 power supply case fan silent

I use Ruideng DPH5005 as a bench power supply and it is quite good for what I need, the only problem I have with it - 5V high speed fan of the original power supply case which runs always, regardless of load/temperature, making a lot of noise.

DPH5005 board has it's own small fan which kicks in only when power supply is overloaded, so probably I could disconnect the case fan completely or connect it to the heatsink fan, but I find no fun in doing so.

There are a couple of suggestions on the Internet how to deal with the noise of the fan - connect it in series of diodes to lover running voltage or to use Normally Open bi-metal thermal switch to turn on the fan at about +45 C.

I liked the latter, but decided to combine it with the first one to limit the driving voltage with a diode. And I had a nice and proven project for that: Madis Kaal tiny_pwm for ATtimy85 microcontroller.

Using pure PWM did not work with this fan - to run the fan stable at the lower speed I had to use quite low PWM frequency with clock divider 128, which was creating extra noise, diminishing the purpose of the project.

As power supply provides 5V, we can use bump-on-the-wire approach to control the fan. Modified schematics looks like this:

Making Bose QC 25 USB friendly

I've been using Bose QuietComfort 25 for a couple of years now. They are great for watching movies on long transatlantic flights, but their miniature on-the-wire microphone and 3mm audio jack makes them unusable for long transatlantic Skype calls. Adding USB capability sounded like a good idea, and it wasn't hard at all with my new Prusa i3 MK3 printer.

For Skype I've been using Plantronics 626 for almost 8 years and finally ear pads started to disintegrate. Instead of soursing a new ear pards for this discontinued headset I decided to used Bose QC 25 as a replacement :)

First make a model in blender3d:

 Then print:

Salvaging temperature and humidity dials

A few month ago my wall clock with temperature and humidity dials feel down from the wall and broke apart.

For the clock mechanism it probably was a good move (I would throw it out of window someday anyway, so loud it was). But temperature and humidity dials were quite useful, so I decided to keep them and reuse some day. And with my new and shiny Prusa i3 MK3 printer this day just came yesterday.

Making Prusa i3 MK3 a bit more stable

A couple of weeks ago I got Prusa i3 MK3 kit as my first 3D printer.

It took me two evenings and a half of Saturday to assemble it. What a nice piece of machinery it is!

I found only a couple of problems with it, first: rubber feet that just wait for any occasion to pop out of the frame when you move the printer.

There are lot of suggestion on Prusa forum how to fix it, using special printed locks, for example, or print completely new feet (what 3D printers are for anyway, if not for replicating and eventually taking over the word).

I've decided to make something myself. And here comes my second problem - last time I used blender3d years ago, so had to spent some time remembering how it works. But after a few trials I eventually got a result with suits me completely. Here it is - a simple shell for Prusa i3 MK3 feet in blender 3d:

Making low-power version of MMR-70

I use modded version of Sony Ericsoon MMR-70 for different projects. It is cheap - less than a euro delivered and in addition to quite capable AVR controller Atmega 32L it has FM radio transmitter with RDS support, 32kHz crystal used together with FM radio and orange LED.

For remote  temperature sensor powered by CR2032 battery I've stripped down all unused components - FM radio transmitter, 2.8V regulator, I2C pull-up resistor, transistors connected to UART pins... So in Sleep mode MMR-70 board with RFM12BS transceiver and BMP180 as temperature sensor takes less than 8uA.

 

Pic. 1. MMR-70 with FM radio chip and I2C pull-up resistors removed. UART, I2C bus and some Digital/Analogue pins exposed to round header sockets. 32kHz crystal patched to Atmega32 for real-time clock support.

MMR70-mod code on Github.

Making Sony Ericsson MMR-70 breadboard friendly

I continue to play with Sony Ericsson MMR-70 board. So far I've done a few iterations on making it breadboard friendly using round header strips. I've started with round pins, but then switched to round sockets - sockets are easier to manage and it produces lower profile. Much more useful than the very first attempt :)

Pic1. On the left - version with round strip pins, on the right - sockets. Board on the right also is very low-power version - all components which are not needed unsoldered to save power when MC is in Sleep mode.

Pic.2 Round sockets (bottom) profile is lower than pins (top).

Sony Ericsson MMR-70 Modding (Part 2)

Modded version of Sony Ericsson MMR-70 now supports SHT1x temperature/humidity sensors and can display information on SSD1306 driven OLED:

All sources as usual on GutHub.

Sony Ericsson MMR-70 Modding (Extreme this time)

Last year I posted simple LED mod for MMR-70 FM Transmitter. This time it is a bit more exterme as it includes rewriting firmware for onboard ATmega32L microprocessor.

This is how the end result looks like:

Sony Ericsson MMR-70 transmitter LED mod for Raspberri Pi

My Raspberry Pi based Internet Radio/Weather Station is going to get a new feature soon - an FM transmitter. You can buy a discontinued Sony Ericsson MMR-70 FM Transmitter for less than 2 EUR now and it can be connected to Raspberry Pi quite easily. Tobias Mädel has done excellent work putting together a small FMBerry daemon which can control MMR-70 connected to RPi's I2C bus. In this case Raspberri Pi is connected directly to I2C pins on Alps TSMZ1-603A FM transmitter (built on NS741 low power FM transmitter chip). Onboard Atmega 32-M is not used and forced to a sleep state to avoid any control conflicts.

MMR-70 has an LED, but it's connected to Mega32 pin 16, so a bit of high precision soldering is required :) To control the LED we need to solder wire directly to the LED or close to Mega32 pin 16: