Pages: [1]   Go Down

Author Topic: Risks of DIY DC power adapter for cameras: voltage & protection  (Read 938 times)

EinstStein

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 501

This is mostly about film cameras. If your camera can use AA battery, chances are you might be using the rechargeable battery.

You might notice the rechargeable (Lithium Ion) battery is 1.2V while non-rechargeable Alkaline battery is 1.5V. The non-rechargeable Lithium battery (not to  confuse with Lithium Ion) is also 1.2V.
Some camera manual specifically warns to use the 1.5V non-Alkaline battery. I haven't find out why yet.

The film camera I have can use the external battery pack though the dedicated connection. The initial intention is to put the external battery in pocket to warm it under the cold condition. It would be good if it also comes with the DC power adapter to work indoors but unfortunately it does not exist. So I am thinking to make a DIY.

The voltage difference of 1.5V vs. 1.2V and the warning against some 1.5V non-alkaline battery raised the a big concern. What should be the DC adapter output voltage: 4.8V? 5V? or 6V? Since 4.8V DC power adapter does not exist (AFAIK), the choices left are 5V and 6V. Is 5V safer than 6V? Some DC power adapter intentionally mentions its current limiting protection, implies it is something to watch out.

So, in brief, is this is trivial project?  What are the risks of DIY DC power adapter?  how to manage it?


 
Logged

sandymc

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 350
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #1 on: April 13, 2020, 08:12:25 am »

Well, firstly, most rechargeable 1.2V batteries are Li-MH, not lithium-ion.

Assuming you're talking about Li-MH, one issue that leads to manufacturers not recommending substitutions is that alkaline batteries have a gradual voltage falloff when discharged. Li-MH on the other hand are quite stable for a long time, then fall off a cliff. That means that, if the low battery detection in the device is designed for alkaline batteries, it may give you such a short period of warning with Li-MH that you effectively have no warning at all.

As regards PSU voltage, 6V should be fine, assuming a four-cell battery pack. The only danger is potential surge current. Alkaline batteries typically can't deliver much surge current, but a big power supply can. That can result in issues over the long term. But if the device was designed for an external power supply, that shouldn't be an issue. If it wasn't, and you're modifying it, then I'd take steps to limit current when the power supply is first plugged in.
Logged

EinstStein

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 501
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #2 on: April 13, 2020, 04:07:55 pm »

Thanks for the correction.

Can I assume that the extra 0.3V in the Alkaline battery (over rechargeable 1.2V) is meant to "Extend" the usable battery life? that the device only needs 1.2V?

If so, would the 5V be more proper? for example, on a surge, it gives 1v more margin for the over rated power?

The DIY DC adapter is really an off-the-shelf 5V (or 6V) DC adapter but with modified connector,  (modified external battery adapter from the camera manufacturer).
Logged

sandymc

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 350
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #3 on: April 18, 2020, 11:53:37 am »

Well, it's more accurate to say that the battery voltage is defined by the chemistry. Most alkaline battery powered devices are designed to work anywhere in the range of 1.5 down to say 1.1 volts because that's the range of voltage that alkalines put out as they go from full to empty. You can generally use Li-MH batteries as a substitute because their operating voltage range overlaps in the 1.1 to 1.2 volt range. Somewhat of a happy coincidence.
Logged

EinstStein

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 501
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #4 on: April 19, 2020, 08:13:31 pm »

Well, it's more accurate to say that the battery voltage is defined by the chemistry. Most alkaline battery powered devices are designed to work anywhere in the range of 1.5 down to say 1.1 volts because that's the range of voltage that alkalines put out as they go from full to empty. You can generally use Li-MH batteries as a substitute because their operating voltage range overlaps in the 1.1 to 1.2 volt range. Somewhat of a happy coincidence.

My concern is on the camera side.
Normally the electronic device is designed to work with certain margin in the power supply voltage, such as +/- 5% or 10%. Since the battery power device that works with both types battery, from 4.8-6.2v, it seems the nominal voltage is 5.5v, with around +/- 0.7v margin.

I guess either 5v or 6v should be fine for the DC power supply. And 5v has the advantage of long term reliability.
Logged

fdisilvestro

  • Sr. Member
  • ****
  • Online Online
  • Posts: 1794
    • Frank Disilvestro
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #5 on: April 20, 2020, 10:40:02 pm »

And 5v has the advantage of long term reliability.

I'd be curious to know how did you get to that conclusion

And btw, Lithium batteries, non-rechargeable, are 1.5V

EinstStein

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 501
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #6 on: April 22, 2020, 04:01:27 am »

I'd be curious to know how did you get to that conclusion

And btw, Lithium batteries, non-rechargeable, are 1.5V

assume the semiconductor aging effect due to the voltage stress.
 
Logged

ussmillerco

  • Newbie
  • *
  • Offline Offline
  • Posts: 8
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #7 on: May 18, 2020, 02:39:53 am »

How many cells is this camera? Iím assuming itís either 2 or 4 cells. If itís 4cells (4x1.2v- 4.8v) and Iím also assuming the metering of this film camera must be kept to exacting voltages, then might I suggest you seek powering it with a boost converter with a li-ion 18650 3.7v battery, with an onboard charger 4.2v that can charge off a simple usb 5v wall converter. In can output an adjustable voltage you can set via potentiometer between 4.3v and 27v at a discharge max rate of 2amps. Such a circuit exists with all thatís needed is the circuit board, a 3.7 18650 (or 2 in parallel), battery holder, and some kind of box to house it. You need to make the connection to the input of your camera. After adjusting your output voltage to the 4.8v. Once set The circuit outputs the 4.8v (or whatever voltage you set) regardless of whether itís on charger or battery as long as the battery has power. When plugged in via usb, the onboard charger outputs 4.2v to the li-ion battery. Only downside i believe is the circuit doesnít a low voltage cutoff so you just need to make sure it doesnít go dead, as 3.7v li-ions donít live long below 2.5-3v. All this for about 3usd for the circuit board, 4 bucks for a good 18650 battery, and a 99 cent battery holder, oh and a cell phone usb charger which most people already have. Ebays littered with the circuit board Iím describing. If you are interested let me know and Iíll share a link to one. Now if itís 2 cells, or 2.4v then youíll need to go in another direction.
Logged

EinstStein

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 501
Re: Risks of DIY DC power adapter for cameras: voltage & protection
« Reply #8 on: May 30, 2020, 01:27:29 am »

How many cells is this camera? Iím assuming itís either 2 or 4 cells. If itís 4cells (4x1.2v- 4.8v) and Iím also assuming the metering of this film camera must be kept to exacting voltages, then might I suggest you seek powering it with a boost converter with a li-ion 18650 3.7v battery, with an onboard charger 4.2v that can charge off a simple usb 5v wall converter. In can output an adjustable voltage you can set via potentiometer between 4.3v and 27v at a discharge max rate of 2amps. Such a circuit exists with all thatís needed is the circuit board, a 3.7 18650 (or 2 in parallel), battery holder, and some kind of box to house it. You need to make the connection to the input of your camera. After adjusting your output voltage to the 4.8v. Once set The circuit outputs the 4.8v (or whatever voltage you set) regardless of whether itís on charger or battery as long as the battery has power. When plugged in via usb, the onboard charger outputs 4.2v to the li-ion battery. Only downside i believe is the circuit doesnít a low voltage cutoff so you just need to make sure it doesnít go dead, as 3.7v li-ions donít live long below 2.5-3v. All this for about 3usd for the circuit board, 4 bucks for a good 18650 battery, and a 99 cent battery holder, oh and a cell phone usb charger which most people already have. Ebays littered with the circuit board Iím describing. If you are interested let me know and Iíll share a link to one. Now if itís 2 cells, or 2.4v then youíll need to go in another direction.


Thanks for your suggestion, but it sounds vey risky, unless you have done it you yourself.
Logged
Pages: [1]   Go Up