The DM134B 16 bit shift register with constant current LED drivers

I have quite a few DM134B IC’s which are 16 bit shift registers complete with constant current LED drivers built in so I decided to make something useful from them. The chips require minimal components; LED current is simply set via an external resistor which is far better than having to use 16 individual resistors. The snag with these chips is that they are surface mount in the SOP-24 package. So to fit them into a prototype board I bought a SOP-24 to DIP converter and soldered one to it and began to experiment with an Arduino and found that they work just fine with the shiftout and direct SPI functions. Just like any other latched shift register.

One chip behaves like two 74HC595’s in series albeit the output enable is active low instead of active high like the ‘595. I wrote a small demo program that counts from 0-999.9 seconds to test them and had some sample breakout PCB’s made in which an Arduino Nano could be fitted to. They worked well so they will definitely be useful for future projects. The demo board contains two DM134B’s daisy chained driving four 7 segment displays which can be used as a voltmeter, temperature readout or indeed any project that needs a 4 digit display. As mentioned above the demo board has space for an Arduino Nano and pins are broke out onto adjacent headers so that they can be used for another purpose such as analog inputs etc.

Here’s the schematic and photos of the demo board. I’ve kept one but the other four I’ve put on eBay as I’m sure they will be useful to someone. The firmware for the demo board can be downloaded here.

Link to Ebay UK where you can purchase these

Electronic tape measure using HC-SR04 ultrasonic sensor demo code

Also available on my Tindie store

Instructions (PDF describing the operation and pinouts) DM134B PCB instructions









A photo of it working:-