GideonTech.com Forums

  • November 17, 2019, 05:44:03 PM
  • Welcome, Guest
Please login or register.

Login with username, password and session length
Pages: [1] 2 3   Go Down

Author Topic: Charging the Zen Micro with a home-made charger - isolating the problem...  (Read 4003 times)

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174

My current set up: 12v 500mA AC/DC wall transformer feeds a LM7805 voltage regulator (output 5v rated up to 1 A) which in turn connects to the power pins of a usb cord, and the cord is plugged into the Zen Micro. Somewhere along the way a component is failing to hold up its end, causing the Zen Micro to think its charging, but failing to do so (battery level may go up ever so slightly when off (trickle charging?) and apparently doing nothing when the Micro is running.
Apparently each USB port can source 500mA of current, so I don't think its the wall transformer or the regulator not being able to handle the current. However, the process to go from 12v to 5v disappates over half the voltage in the form of heat...
I've plugged a USB light+fan into my device, and it runs perfectly for 10 seconds or so, before it abruptly stops.

If the regulator is the problem, how would I rewire my device to solve the problem?
Logged
LOUD ANGRY NOISES

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com

Is the 7805 getting hot?  You might be tripping the thermal protection.
Logged
"I'm totally going to send ninjas after you." - BalefireX

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174

Yeah, over time while attempting to charge the Zen I notice the case its enclosed in becomes exceptionally warm. I figure this regulator is only ~40% effecient, so perhaps it cannot supply enough current.
Logged
LOUD ANGRY NOISES

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com

Try putting a heatsink on it and running it outside of the case it is in; see if it lets the light/fan combo run longer.
Logged
"I'm totally going to send ninjas after you." - BalefireX

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174

How exactly does the overheat protection circuit work in the regulator? I just tested the circuit, and the regulator is indeed becoming hot quite fast. It is dumping far too much heat to possibly be efficient or useful; the last thing I want to happen is my circuit's enclosure to become steaming hot...
One idea is to have multiple voltage regulators to slowly step down the input, but that sounds like there should be another way. The enclosure it is in is tiny, so I am slightly pressed for space.
Logged
LOUD ANGRY NOISES

njbrad

  • GT Fanatic
  • **
  • Karma: +2/-1
  • Offline Offline
  • Posts: 99

Try a lower voltage power supply.  If I recall correctly the 7805 will drop a minimum of 1.5 volts.  A 6.5 - 7 volt power adapter should work.  (And the regulator should be a lot cooler)

Brad Bruce
Logged

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174

Well if that's the case - why not just get a 5v wall ac adapter? There must be some way...
Logged
LOUD ANGRY NOISES

Excess3

  • Senior Modder
  • ***
  • Karma: +1/-0
  • Offline Offline
  • Posts: 586

If your voltage regulator has been getting that hot it may now be damaged, thus making things worse.  Do you have another one lying around?  If so, try replacing the IC and put a heatsink on it this time, don't forget the thermal paste.
Logged

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com

Well if the thermal protection is kicking in, the circuitry of the 7805 should be just fine.  The lower voltage power supply might work, as would just sinking the thing.
Logged
"I'm totally going to send ninjas after you." - BalefireX

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174

I guess no matter what method I use, the 7 volts would have to be converted as heat?  :roll: Unless... I have a few LEDs on there to drop the voltage? Suggestible if its drawing that much current?
Logged
LOUD ANGRY NOISES
Pages: [1] 2 3   Go Up
 

Page created in 0.057 seconds with 19 queries.