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--- raspberrypi:sdcardcorruption [2013/08/24 09:03] – created rlunaro
+++ raspberrypi:sdcardcorruption [2022/12/02 21:02] (current) – external edit 127.0.0.1
@@ Line 8: / Line 8: @@
   * March 2013: a technique to avoid data corruption by [[http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=36533|making regular checks on the sd card]]
+===== ¿problem in the power source?? =====
+I was using as a power source for the Raspberry PI an spare micro-usb charger. In fact, I've switched among chargers thinking that they were interchangeable. After this problem, I've made several investigations:
+  * I grabbed a [[http://www.ebay.com/itm/UNI-T-UT71C-Intelligent-Digital-Multimeter-UT-71C-AC-DC-LCD-Meter-Power-Detector-/281161268334|good multimeter]]: I don't want to hear that I've didn't using the proper tools
+  * I measured the voltage and the current of the charges I had at home. These are my conclusions:
+    * The chargers are very different in their specifications (they all have 5V output, but the current varies from 300mA to 700mA or even 1A). I've checked that my raspberry (Model B) admits 700 mA, so I think this could work
+But...
+===== I was using chargers, not power sources!!!!! =====
+One thing I've discovered is this:
+  * The real output voltage is 7.5 V on average ((I've tested many of them)), not 5V as especified. Probably this is because of my power line, but it might be also because most of these chargers aren't regulated, with internal electronics to send 5V no matter what input voltage they receive.
+  * __CORRECTION: The following is not true, probably this behaviour is because most of them have a protection against short circuits.__ They send the power in waves: they sent a wave of 300mA of power, and they stop for a while. Then, start again. At the very first moment I've though that I've was measuring wrong, but not: I've double checked this with another multimeter and the same result. **They send and stop, send and stop.** This is a shot in the head for a computer (however small may be, as the raspberry), and the perfect recipe for a disk crash (like I had).
+===== A fresh start =====
+I've bought a new card (27-sept-2013) and started again. However, there are some changes in my configuration that worth mention. Let's see if this solve the problem or not.
+==== UPS on the rescue ====
+The previous model was pluged directly to the power source, and I have to admit I had several blackouts. It could be the cause of the corruption??? It is not clear.
+However, with this new model, I've installed also a [[raspberrypi:blackoutdetector|blackout detector]] that sends me a message when the house is out of power and also, after 25 minutes, shuts the Raspberry Pi down, so I think possible problems related with power are removed from the equation.
+==== New power source ====
+I've bought a 1A (1000 mA) power source with 5V output. Ok, let's be true: it was sold in the supermarket as "charger", but it cost 15 euros instead of the usual 5 euros a cheap one usually costs.
+I've measured it and it's regulated: it gives 5V despite of the consumption of the device, or (I guess) the power source of the house.
+You can get one of this [[http://es.farnell.com/raspberry-pi-psu/rpi-psu-eu-mk1/power-supply-raspberry-5v-1a-euro/dp/2254794|from farnell]], but the problem with farnell is that you have to spend at least 25 bucks per shipment.
+After this, the board is running well, but __it's too early to reach conclusions__; lets give it some time.
+===== More on this topic =====
+Checkout the [[http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=51436|this thread]] and you will find a
+[[http://d4c027c89b30561298bd-484902fe60e1615dc83faa972a248000.r12.cf3.rackcdn.com/supporting_materials/Raspberry%20Pi%20Start%20Guide.pdf|start guide]] who says the following:
+//The unit is powered via the microUSB connector (only the power pins are connected, so it will not
+transfer data over this connection). A standard
+modern phone charger with a microUSB connector
+will do, providing it can supply at least
+**700mA at +5Vdc**. Check your power supply's ratings
+carefully. Suitable mains adaptors will be available from the RPi Shop and are recommended if you
+are unsure what to use. //