Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Banart on October 28, 2017, 02:32:18 AM

Title: Try to attach a little (~400mA) motor in this schematic but it doesn't start
Post by: Banart on October 28, 2017, 02:32:18 AM

I am a  programmer and I recently began studying some electronics & AVR programming.

I am trying to use a step down voltage regulator (LM2678-5.0 datasheet (http://www.kynix.com/uploadfiles/pdf2286/LM2678S-5.0.pdf)) to transform battery voltage (9/12V) into a suitable 5V. I am not using a simple LM7805 since this is part of a bigger robotic project, where I need to transform more than 1A, and it would be nice to spare energy (=less battery weight).

I built this schematic (photos below); with a 10kOhm load I get 5.02V; but as I attach a load to it, voltage drops. As example, as I attach a 20mA led, I get about 3V. I tried attaching a little (~400mA) motor, but it doesn't start (there's no voltage!).

Any suggestions? Thanks in advance

(http://www.kynix.com/BlogImage/WXjHS.png)
(http://www.kynix.com/BlogImage/xfcPO.png)
(http://www.kynix.com/BlogImage/hvQCm.png)

BTW,the inductors and capacitors has been chosen accordnigly to Texas Instruments online simulation tool.