Category Archives: Aggregated

Free PCB Sunday: Pick your PCB

via Dangerous Prototypes


We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Be sure to use a real e-mail in the address field so we can contact you with the coupon.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.
  • PCBs are scrap and have no value, due to limited supply it is not possible to replace a board lost in the post

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App note: Selection of three locations of current sense resistor in buck converter

via Dangerous Prototypes


Sensing current utilizing MOSFET’s Rds(on) and Inductor’s DCR in different location discussed in this app note from Alpha and Omega semiconductor. Link here (PDF)

In current mode converters, current sense resistor can be placed in three locations: input loop, output loop and freewheeling loop. The pros and cons are discussed in details. The principles and features of peak current mode and valley current mode are also presented. The cautions and tips for using Rds(on) of high-side MOSFET, low-side MOSFET and DCR of the inductor as the current sense resistor are also mentioned at the end.

App note: Paralleling power MOSFETs in switching applications

via Dangerous Prototypes


Application note from Alpha and Omega semiconductor on proper design of circuit and PCB layout to balance parallel MOSFETs. Link here (PDF)

This paper discusses issues involved in paralleling MOSFETs in high-power, high-frequency switching applications. It investigates root cause problems such as unbalanced voltage and current by taking a closer examination of PCB layouts and important circuit design parameters for driving paralleled MOSFETs

Keeping the LiPo Smoke Where It Belongs

via Hackaday » hardware

Nothing brings joy to a hacker’s heart like taking a cheap gizmo and making it useful. Over at [AndyHull] popped open some cheap LiPo battery power packs to see if he could power a Canon Powershot camera. The entire shebang would be left in the wilderness for photography so keeping it inexpensive was a big goal since it might be destroyed or lost.

The power packs [Andy] looked at have a TP4221 controlling the charge cycle for up to four 18650 LiPo cells connected in parallel. The controller also boosts the voltage to 5 volts for one or two USB ports while providing automatic shutdown if the LiPo cell voltage drops below 3.2v. Below that voltage the cells can be damaged and might possibly cause a fire.

The packs [Andy] used also had a torch output to drive an LED almost directly from the cells. That output is a nominally 3.8 V at 100 mA which is just what he needed to power the Canon Powershot. It could be used to power small micros or other low power devices.

The LED was removed and replaced by a connection to outside the pack. The torch output is triggered by two quick presses on a switch that was also replaced with a connector to allow remote control.

If you’re looking for powerful battery options, give LiPo a try and have a look at [Andy]’s LiPo battery safety issues post, also on For a broader LiPo overview, see this obsessive rundown of various batteries.





Filed under: digital cameras hacks, hardware

App note: Introduction to hearing aids and important design considerations

via Dangerous Prototypes


Introduction to hearing aids app note (PDF!) from Maxim:

This application note introduces the styles of hearing aids, including behind the ear (BTE), in the ear (ITE), in the canal (ITC), and completely in the canal (CIC), as well as a brief summary of both analog and digital hearing aid technologies. Also discussed is the importance of the audio-processing path, the functions of electrical components, and some critical elements that designers must consider when selecting products.