====== Power supply for Pentax K20D/K10D/K7 ======

There are situations where you need power supply, for example to take night shot with long exposure, here's a shot description who to fast and relatively cheap make power supply for Pentax camersa (K20D/K10D/K7) and perhaps other models as well. WARNING! I can't guarantee that everything here is correct and that it will not damage your camera, always double check everything. I make this device for myself and it works perfectly.

Alternatively you can buy cheap power supply for Canon CA-570 on eBay or any other auction service and mout Hirose connector.

Original power supply costs over 120 USD.

===== Parameters =====

Power supply should give 8.3 V, maximal current: 2 A (basen on: [[http://www1.fr.shopping.com/xCC-adaptateur_secteur_pentax-digit_photo_com_merch|this shop's site]]. As input power it's best to use power supplies used in laptops, they're compact and they can support high current and they're relatively cheap and voltage stabiliser. As voltage stabiliser I used [[http://www.st.com/stonline/products/literature/ds/1356.pdf|L4960]], it has wide input voltage, high current (2.5 A) and is relatively cheap. You can buy [[http://sklep.avt.pl/p/pl/40049/miniaturowy+stabilizator+impulsowy+-+zestaw+do+samodzielnego+montazu.html|complete kit in AVT (AVT-1081)]] - costs 13 USD (without shipment), [[http://sklep.avt.pl/p/pl/40048/miniaturowy+stabilizator+impulsowy+-+plytka+drukowana.html|PCB itself]] costs less than 2 USD.

===== Costs =====

Costs: laptop power supply - about 15 USD, voltage stabiliser - 13 USD, [[http://www.hirose.co.jp/cataloge_hp/e20609504.pdf|Hirose MQ172-3SA-CV(50) plug]] - 4 USD [[http://pl.farnell.com/hrs-hirose/mq172-3sa-cv-50/plug-we-wy-3way/dp/1518737?Ntt=MQ172-3SA-CV%2850%29|Farnell]] or 3 USD [[http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=H10485-ND|Digikey]].

===== Design =====

Schematics and PCB board can be found on [[http://www.st.com/stonline/products/literature/ds/1356.pdf|page 9. of datasheet]] for L4960. Below is a part of this page, almost identical schematic is used in AVT kit (AVT-1081) mentioned above, I added resistor value for 8.3 V:

{{:elektronika:zasilaczpentaxk20d:l4960-p9.png|Stabiliser for 8.3 V}}

You must set output voltage to 8.3 V - for schematics above: R4 = 3 kΩ, for AVT-1081 kit: R3 = 3 kΩ. In case of AVT kit you must drill holes for radiator. Below is a picture with pinout for special plug (based on [[http://www.flickr.com/photos/nebarnix/1166654613/|zdjęcia z flickr]] and self study):

{{:elektronika:zasilaczpentaxk20d:pentax_plug.jpeg?650|Pinout for power plug Pentax K20D/K10D/K7}}

===== Tests =====

After assembling AVT-1081 kit I powered it with 15 V and loaded with 1.8 A on 8.3 V side (lightbulb). Output voltage dropped to 8.1 V and after 15 minutes radiator was worm (you could still touch it without risk of burn). After connecting camera (Pentax K20D) it used about 0.3 - 0.4 A during normal operation. I also changed input voltage from 12 V to 15 V, voltage stabiliser still gave 8.3 V. Device worked perfectly during few hour test with long exposure.

Below few photos of power stabiliser and special plug:

{{gallery>:elektronika:zasilaczpentaxk20d?zasilacz*&lightbox}}

===== Links =====

Links:
  * [[http://roamingdrone.wordpress.com/2008/09/26/diy-ac-adaptor-for-the-pentax-k10d/|Power supply based on linear stabiliser]] (disadventage: it can get hot when using higher input voltages),
  * [[http://www.flickr.com/photos/nebarnix/1166654613/|oryginal photo with pinout]].

~~DISCUSSION~~