Vivitar 2800 Charging Profile Data, (Single board operation with and without Neon Bulb) Options

[dkirk]

There have been numerous questions about the charge rate of the 2800, so I went ahead and tested it under the following conditions.

Test Conditions :
4 NiMH batteries as the power source (Average Open Circuit Battery Voltage = 5.3 Vdc)
470 K resistor installed to disable auto off feature
One board operation (2800A board, all other boards removed)
With and without Neon Bulb
With and without a 0.47 ohm wire wound resistor in series with the battery

(Note : removal of the Neon Bulb disables the charge control/regulator of the 2800 and causes the inverter to run continuously and this can be seen in the plot below)

Below is the plot showing the results (also attached is the .pdf version of the plot)
 Vivitar_2800_Charging_Profile.jpg ( 174.25K ) Number of downloads: 39

 Vivitar_2800_Charging_Profile.pdf ( 13.8K ) Number of downloads: 11


Picture below shows the single board configuration of the Vivitar 2800 using the 2800A board for the above tests.
 100_1306elowres.jpg ( 128.6K ) Number of downloads: 24


Enjoy,
Don

[212]

Sir...I hope it is OK to call you that...very good work:)

I have seen several cases where one 2800 can outperform another by a pretty wide margin. The one you have seems to be one of the lesser ones. I would love to remove the neon lights on all mine, but some will charge to an uncomfortable high for me. I wonder if there is something we can do about limiting the voltage even with the light removed, on the ones that need it?

[oddball64]

When you say, "add the .47 ohm resistor in series with the batteries," what would that look like. I would assume it be in line with one of the wires going to the battery but I thought that was parallel. I don't see how else to wire it in. I'm not correcting anyone, I just don't know what the heck I'm doing.

[dkirk]

When you say, "add the .47 ohm resistor in series with the batteries," what would that look like. I would assume it be in line with one of the wires going to the battery but I thought that was parallel. I don't see how else to wire it in. I'm not correcting anyone, I just don't know what the heck I'm doing.

Oddball,

You are correct. The 0.47 ohm resistor that I mentioned is just placed in line with "one" of the wires coming from the battery pack. If you connected one end of the resistor to the black wire from your battery and the other end of the resistor to the red wire from your battery, you would be connected in parallel with the battery.

When using 4 NiMH batteries with the Viv 2800 you probably don't need the series resistor because the Viv 2800 appears to be of a much more robust design than the recent Viv 2000 units that have the DF500 boards (but you still might need the 0.47 ohm resistor if the slave controller you are using can't handle the high inrush current).

The Viv 2800 inverter transistor has much better current handling capability than that found in the recent Viv 2000 units.

Don

This post has been edited by dkirk: Aug 16 2006, 11:32 AM

[oddball64]

Well, that's good to hear that the 2800 is a more "robust" unit because I got another one since I fryed my first one. It helps when you do the wiring right the first time. But it is fun to "learn" how to do this on my own, thanks to all the great people here. You're doing a great job, Dkirk, at getting these flash units figured out for us. I've almost got one ready to turn on but am still a little hesitant, due to the possibility of smoke.

[aparham]

When using 4 NiMH batteries with the Viv 2800 you probably don't need the series resistor because the Viv 2800 appears to be of a much more robust design than the recent Viv 2000 units that have the DF500 boards (but you still might need the 0.47 ohm resistor if the slave controller you are using can't handle the high inrush current).
Don

Don,
Wouldn't a choke (inductor) work better than a tiny resistor in limiting in-surge current? Does a "wire wound" resistor, in effect, provide some inductance? Just thinking out loud...

This post has been edited by aparham: Aug 17 2006, 07:04 PM

[dkirk]

When using 4 NiMH batteries with the Viv 2800 you probably don't need the series resistor because the Viv 2800 appears to be of a much more robust design than the recent Viv 2000 units that have the DF500 boards (but you still might need the 0.47 ohm resistor if the slave controller you are using can't handle the high inrush current).
Don

Don,
Wouldn't a choke (inductor) work better than a tiny resistor in limiting in-surge current? Does a "wire wound" resistor, in effect, provide some inductance? Just thinking out loud...

[aparham]

When using 4 NiMH batteries with the Viv 2800 you probably don't need the series resistor because the Viv 2800 appears to be of a much more robust design than the recent Viv 2000 units that have the DF500 boards (but you still might need the 0.47 ohm resistor if the slave controller you are using can't handle the high inrush current).
Don

Don,
Wouldn't a choke (inductor) work better than a tiny resistor in limiting in-surge current? Does a "wire wound" resistor, in effect, provide some inductance? Just thinking out loud...

Uh, is there an answer here somewhere?

[dkirk]

When using 4 NiMH batteries with the Viv 2800 you probably don't need the series resistor because the Viv 2800 appears to be of a much more robust design than the recent Viv 2000 units that have the DF500 boards (but you still might need the 0.47 ohm resistor if the slave controller you are using can't handle the high inrush current).
Don

Don,
Wouldn't a choke (inductor) work better than a tiny resistor in limiting in-surge current? Does a "wire wound" resistor, in effect, provide some inductance? Just thinking out loud...

Hello Aparham,

Don't really think the 0.47 ohm resistor is even needed with the Vivitar 2800 since it has a much more robust inverter transistor, but it is good insurance.

Yes, I actually prefer the 0.47 wirewound resistor because it does offer a little bit of inductance. Not sure how effective pure inductance would be because the in rush current is actually pretty long in duration on the Vivitar 2000 with the DF500 board due to the large flash cap (800ufd), so in effect it looks almost like a short circuit for a somewhat long period of time (not just a sharp spike).

I have actually been playing around with a very simple "soft start circuit", but hate to add complexity. With my control board I have played around with just adding a series gate resistor, and a capacitor from the gate to ground on my mosfet that charges my flash, and this causes the gate voltage to rise slowly trough its threshold voltage, and this does a wonderful job of controlling the inrush current but with this simple system it eats up too much time getting up to the threshold voltage. This is not a problem if you are running with 30 second charge times, but I am running with 10 second charge times to allow a picture every 10 seconds.

My Vivitar 2000 flash in the field right now (DF500 board version) is using a non wirewound 0.47 ohm 2 watt resistor, and it has fired hundreds of times without any problems.

Great question about the inductance, and it really should be investigated in more detail.

Don

This post has been edited by dkirk: Aug 17 2006, 08:56 PM

[dkirk]

Sir...I hope it is OK to call you that...very good work:)

I have seen several cases where one 2800 can outperform another by a pretty wide margin. The one you have seems to be one of the lesser ones. I would love to remove the neon lights on all mine, but some will charge to an uncomfortable high for me. I wonder if there is something we can do about limiting the voltage even with the light removed, on the ones that need it?

Hello 212,

Yep, I noticed that the Vivitar 2800 that I plotted the chrage profiles on was not a monster (did not charge to as high a voltage as others I had previously tested).

At some point in time I will go back and look at other ways we might be able to control the voltage from getting too high on these guys when running them open loop (when running with no Neon light which causes it to run wide open without the internal circuit that controls/limits the charge).

Don

This post has been edited by dkirk: Aug 19 2006, 05:01 AM