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Forum: Pentax DSLR Discussion 01-11-2009, 03:42 PM  
K200D Battery Meter Problem
Posted By dmessing
Replies: 34
Views: 38,076
Vincent and all Others,

I appreciate the graph updates. Knowing what I know now, they make a huge amount of sense. I am also glad to know Pentax was not to conservative on the battery monitoring and actual cutoff. In fact, I think they took it to beyond what I would have personally designed.

It was just due the poor performance of my Engerizer 2550 mAHr batteries with nearly 1.5 amp draws.

I am looking forward to the new Sanyo Eneloop batteries from Amazon, scheduled to arrive tomorrow.

I really wish to thank each and every person that lead me to the correct battery source. Obviously through many hours of trial and error, it comes down to what works.

I was curious if any company manufactured a Li-ion like used in my Nikon and in laptop computers built in a rechargeable AA package. So far none have turned up my searches. That seems to be some of the best capacity in a given physical size.

I saw a posting under another heading about someone wanting to build their own external power supply. I have built many power supplies, but when it comes to powering something as expensive as this camera, one would need to consider extra circuit design in the power supply to protect from over voltage with a crowbar circuit and a current limit circuit. Good sources for already built regulated supplies are Allied Electronics and Mouser Electronics.

Another gotcha I had with an expensive 900 mHz Ethernet modem at work was connecting and disconnecting the power plug with the power supply powered on. A small arc is created at time of connect and disconnect creating spike that fried an internal voltage regulator. I never connect or disconnect to a device with the voltage on, especially after that. Some companies do a good job in protecting internal circuitry form such action, others don't. During this past week when I tested the camera current using the external connector, the 5 mm OD x 2 mm ID plug was intermittent. I quickly stopped and found a plug that was tight.

For whats it worth.
Forum: Pentax DSLR Discussion 01-11-2009, 12:54 PM  
K200D Battery Meter Problem
Posted By dmessing
Replies: 34
Views: 38,076
Thank you Vincent for the kind words.

With the adjustment on my power supply, I was able to hit all voltages, but there was a spot on the Voltage Adjust Control that would not let me hit exactly 4.7 volts. You will see that is missing on my list. I could have made an external voltage divider circuit, but didn't take that extra time.

The camera monitor circuit has a dampening feature. That monitor circuit has to be the one that drives the monitor up to the point it also trips off the camera. Without an average of the value, the would be tripping off all the time. Once the camera trips off it stays off until power is recycled. Between functions such as shutter and flash spikes, the result needs to be smooth. I think this is where it is hard to track with a quick result.

As capacity drops, voltage sags.

If a power supply that has a current limit feature, when the current limit is reached, the voltage begins to drop.
Forum: Pentax DSLR Discussion 01-11-2009, 11:51 AM  
K200D Battery Meter Problem
Posted By dmessing
Replies: 34
Views: 38,076
From what I see, the voltage level does have a major result on the battery monitor. The Turn On current draw each time the camera comes on is exactly the same. By changing the voltage output upward or downward and cycing the camera back on, the level at which the battery monitor shows full to empty repeats with the same results. Below a certain voltage the battery monitor is empty the camera operates until it sees the cutoff voltage and shuts off.

I believe 4.7 Volts total, (1.175/Cell) and above the monitor is Full.
4.6 to 4.7 volts (1.15 to 1.175/Cell) camera still works monitor is Empty
4.6 Volts and less (1.15 Volts/Cell) camera is off line

I think what is a little deceiving it appears the camera has a large value capacator that holds the voltage level at a certain level and the voltage monitor doesn't quickly track it.

I hadn't given this as much emphasis as to what voltage the camera fails to operate. My main concern does the camera operate at less than 1.2 volts per cell, 4.8 volts total, and yes it does. With any supply be it AC powered or battery supply a certain voltage is needed , if the capacity is low then the voltage quickly sags under load.

Could be the camera has two circuits providing the battery monitor operation. It would amount to both a voltage value and a current value.

For the camera circuits to measure a current value, the current flow would have to be converted to a voltage for the circuit to measure it. A current measurement is accomplished by a drop across a very low impedance such as .1 ohm. Ohms law for a value of current drawn is voltage divided by resistance.

There is really no need for both to be measured. If the capacaity of the supply is weak, the voltage will immediately be weak under that load.
Forum: Pentax DSLR Discussion 01-11-2009, 10:58 AM  
K200D Battery Meter Problem
Posted By dmessing
Replies: 34
Views: 38,076
I wanted to learn the following about my K200D, the cutoff battery voltage/monitor reading, and current drawn during different functions.

The batteries in the camera are in series. The battery toward the lens side of the camea is the plus, the battery 3rd from the lens side is the minus. There is a small switch activated when the battery door closes, that must be pushed in to power up the camera.

Here is what I observed:

Batteries were out of my camera for several days I placed fully charged batteries in the camera, camera wouldn’t turn on. Put those in the Maha charger and noticed they were full. Put in the second set and camera still didn’t turn on. Within a minute, tried the camera again and it came on with no problem. It was like there was a large capacitor that had to charge first???

I was able to connect directly to the battery clips, pushing in the little switch, the camera came on. I had a 25 amp adjustable supply allowing voltages down to 1 volt. I started with at 5.2 volts and zeroed in on 4.8 volts. I watched the voltage with two digital meters at the supply output both were exactly the same. The Beckman 223 reading is the left value/Fluke 87 is the right reading

4.59 Volts NO Turn On
4.60/4.596 Turns ON, Shutter trips every time, Flash charges and works
4.65 volts Camera Came On, Bat Monitor Empty
4.69 volts Camera Came On, Bat Monitor Empty
4.73 volts Camera Came On, Bat Monitor Full
4.76 volts Camera Came On, Bat Monitor Full
4.78 volts Camera Came On, Bat Monitor Full
4.79 volts Camera Came On, Bat Monitor Full
4.8 volts Camera Came On, Bat Monitor Full

Here is what is very interesting. If I very slowly started turning down the voltage, the battery monitor didn’t change from full, even if the power supply was down to 2.6 volts. It was like a charged capacitor was maintaining the operation. In order to catch the threshold, the supply voltage was adjusted a small fraction, the bottom switch was depressed and it then would show the difference after camera came on.

Turn ON is 4.60 volts. I tripped the shutter 4 times, popped up the flash tripped shutter two, it worked every time with no flicker on the 4.60 volts supply. ON MY CAMERA 4.60/4.596 VOLTS IS THE LIMIT LOW, STILL WORKS AT THAT VOLTAGE! Readings shown are a Beckman reading on the left and Fluke on the right.

Never saw half a battery monitor, ever. Above 4.72/4.715 Battery Monitor was full. The above voltages were straight from the power supply, no measuring resistance in series.

The Current Draw Measurements were made at about 5.2 volts, with a lab type HP 0.1 ohm shunt for converting mA to mV for the Scope meter and double checking that with the Fluke 87 in series. The Fluke 87 was set for Record in Min Max with 100 mS capture. The HP 0.1 ohm shunt fed a Fluke Scopemeter for comparison of accuracy, both the same readings.

Functions of the K200D:

Turn camera on: Quick short spike of 1296 mA ( within a second)
First Stage, Camera On, LCD Screen On, 260 mA
Second Stage, Camera On, LCD Screen Off 149 mA for about 10 seconds
Third Stage, Camera On in standby 87 mA
Fourth Stage Sutter Tripped 1.484 mA for less than a second
Flipped up the Flash and Charge, for a brief moment 1.480 mA
I used two digital meters, the Beckman 223 and Fluke 87B. Where the above voltage reading are shown, i.e. 4.60/4.596 those are from the Beckman and the Fluke at the output of a 25 amp voltage regulated/adjustable dc power supply.

I didn't write it down, but it seems during a 30 sec time expose, after the initial quick 1484 mA spike, the current draw was 400 mA with shutter open.

I wish to thank UnknownVT who collaborated with me all week and corrected my typos and gave me additional ideas. The part that was confusing at first is getting past a point where the camera needs a short time after power has been removed to establish a point where it will turn on.

Not a part of these measurements shown above, but FYI only. Regarding the connector for an external power supply, I was surprised how many styles and sizes are listed in Wikipedia. Those in the US, Germany, Din, Japan all are different. A 5mm OD 2mm ID easily goes into the camera, but the I.D. is too big creating an intermittent connection . Closest to what I could purchase locally from Radio Shack was the Adaptaplug “C” part # 273-1706. Its size is listed as 4.7 mm O.D. 1.7 mm I.D. These are made plug on their power supplies. I soldered two wires onto the plug and tested with an external power supply and it had no signs of being intermittent.

Dave
Forum: Pentax Camera and Field Accessories 01-03-2009, 02:55 PM  
Remote control
Posted By dmessing
Replies: 18
Views: 4,551
I was trying my remote controls and found the Sony RMT-814 remote that came with the Sony DCR-TRV740 Digital Handcam works. The DISPLAY button and the reverse double-arrows for Search Mode, will trigger shutter on the K200D

dmessing
Forum: Pentax DSLR Discussion 01-03-2009, 12:51 PM  
K200D Battery Meter Problem
Posted By dmessing
Replies: 34
Views: 38,076
Before, I do any current draw measurements and capturing instantaneous current peaks down to the millisecond range, I wanted to verifiy if the batteries are used in series configuration.

The batteries appear not be in a single, straight series only configuration, here is what I found.

Laying the K200D upside down with the lens pointed away from me, I numbered the battery compartments in the following manner. Most foward was #1, going CCW, #2, then #3, then #4. Using an ohmmeter I found #2 and #4 are a direct short (a jumper internal inside the camera).

Then using the same numbers for the battery cover, it is plain to see a jumper between #1 and #2 and a jumper between #3 and #4.

Drawing that out, #1 down in the camera is the most positive voltage source of battery pack and #3 is the most negative source.

Then using a regulated power supply I connected a range of 4.8 to 6 volts positive to #1 in down in the battery compartment and the negative to #3.

The camera would not turn on.

That seems to indicate the camera is using a connection at the #2 to #4 internal jumper at half voltage potential.

If it were just a true parallel connection, then the camera should come on with just two batteries at the #1 and #2 slot, or two batteries only at the #3 and #4 slot.

I would be interested in thoughts on this before I proceed to current measurements, which may clear up some of this.

dmessing
Forum: Pentax DSLR Discussion 01-03-2009, 08:57 AM  
K200D Battery Meter Problem
Posted By dmessing
Replies: 34
Views: 38,076
Thank you for the great replies. I am now curious if the set point for my K200D battery depletion is 1.19 per cell. That is a valid setpoint. Using a good regulated power supply I should be able to slowly take the voltage down to 4.76 volts showing where the trigger for battery depletion appears.

I agree the only way to check remaining capacaity is to measure the current drain with time.

Using a Fluke Scopmeter, in record mode, record current draw with time in m/sec, I plan to see what the actual current draw is for each function of the camera's operations when shutter operates, the LCD screen displays and flash operation/recharge. We will be able to calculate draw against time using actual camera operation. With that information, it will become known what the draw is and for what peroid of time. I hear the comments about the high current demands of digital cameras, is there data of what that current draw is for each camera function??
Forum: Pentax DSLR Discussion 01-02-2009, 08:41 PM  
K200D Battery Meter Problem
Posted By dmessing
Replies: 34
Views: 38,076
I am an Electronics Specialist with experience to 1958. I too find the K200D showing a premature "depleted battery" message using 2450 mAh Energizer batteries. After the K200D shows a battery depletion, I removed and checked the batteries using a 2 ohm load resistance across each cell with an accurate, high-end digital voltmeter. Each battery had a reading no lower than 1.24 volts. The nominal voltage of a Nicad or NiMh is 1.2 volts. What I found, the batteries had a huge amount of capacity left. They had not yet achieved the nominal 1.2 volts of the battery. This means the Pentax software is set too high for for a 1.2 volt battery. Pentax needs to get this fixed. I use a Maha MH-C801D charger that charges each battery separately.

Pentax....get your software fixed and issue a firmware update. Do like Garmin does with their GPS units. Make a screen entry allowing user choice between battery types offering a proper setpoint in the software.

D Messing
Nebraska City
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