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hardware:autopoweron 2009/08/31 08:56 hardware:autopoweron 2017/09/06 18:38 current
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Here's a circuit using a NE556N dual timer IC that automatically turns the DNS-323 on whenever power is first applied or re-applied after power failure.  This circuit is applicable to the DNS-323 hardware version B1: Here's a circuit using a NE556N dual timer IC that automatically turns the DNS-323 on whenever power is first applied or re-applied after power failure.  This circuit is applicable to the DNS-323 hardware version B1:
{{  hardware:delayed_on_pulse.png  |Delayed turn-on circuit}} {{  hardware:delayed_on_pulse.png  |Delayed turn-on circuit}}
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If you are successful, whenever the power is plugged in the DNS-323 should automatically turn on after about ten seconds. If you are successful, whenever the power is plugged in the DNS-323 should automatically turn on after about ten seconds.
 +~~CLEARFLOAT~~
 +===== Other solutions =====
 +There is also another auto turn on circuit available, [[http://www.waggies.net/Ken/dns323/index.htm |this one using a hex inverter]].
 +====== Single capacitor solution (B1 hardware) ======
 +**Background info:** The power on button is connected to pin 1 of HT48R05A-1 (U25) and has a weak 120k pull up.  The H48R05A-1 is an 8 bit micro-controller from Holtek which conveniently handles very slow rise time inputs. 
 +
 +**Solution:** With such a weak pull up value, all you need is a (fairly large) capacitor to delay the rise time, which tricks the HT48R05A-1 in thinking the power button has just been released.
 +
 +
 +===== How to do the mod =====
 +
 +  - Disassemble your DNS-323 (4 screws on the front, 4 screws in the back, another set of 4 screws in the back, and you're done).
 +  - {{  hardware:power_on_switch_bottom.jpg?300|}} Solder a 150uF (6.3V or higher) electrolytic capacitor between the ground (circled in black) and the power on pin (circled in red). 
 +    * **__NOTE: electrolytic capacitors are polarized!!!__**
 +    * Make sure the negative is soldered to ground (the side of the capacitor will have a large stripe next to the pin).
 +    * About the capacitor... I am pretty sure a lower value (ex.: 68uF) will also work, but I didn't try.  I have a feeling high ESR capacitors are better since a 15uF __unpolarized__ capacitor (used for AC relays) worked fine yet it's 15 uF electrolytic equivalent didn't.
 +  - Reassemble your DNS-323 and enjoy. 
 +
 +**Note:** The power switch still works to power off the unit, and to power it back on if it was powered down by the switch or by software shutdown.\\
 +
 +\\ **Limitations**
 +  * Doesn't work for power glitches (anything below 3-4 seconds). 
 +    * {{  hardware:power_on_optional_diode.jpg?300|}}**To fix this limitation**, you can put (in theory since I didn't try it) a diode in parallel to the weak pull up (R209, which is near U25).  When the 5V rail fails, the capacitor should discharge very quickly.  The N side of the diode should be near the "R" of "R209".
 +    * If you are serious about your NAS, it should be on a UPS (which filter glitches) and therefore you don't need to add a diode...
 +
 +~~CLEARFLOAT~~
 +**Assembly pictures**\\
 +I stole an electrolytic capacitor from a unused electronic circuit.  The leads weren't long enough, so I had to use wire.  The electrolytic capacitor you'll buy will likely have leads long enough so you won't need to go through this hassle. (But make sure that non-isolated leads don't touch front panel after assembly. The panel is actually made of (anodized) aluminum and there can easily be a short-circuit, leading to router powering down soon after start up - or worse.)
 +\\ {{hardware:power_on_capacitor.jpg?300|}} {{hardware:power_on_final_result.jpg?500|}}
 +~~CLEARFLOAT~~

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