Vivitar 2000 Slave (DF500 board version), Technical Data (neon light, series resistor, battery voltage) Options

[dkirk]

There have been numerous questions regarding the Vivitar 2000 slave flash, and I have therefore started to dig into some of the topics of interest (DF500 board). While some of this posting will only be understood by the electrical jocks, some of the information should be helpful to those looking to use a Vivitar 2000 flash unit.

Neon Light Removal Test
Attached is a chart showing the discharge characteristics of the flash capacitor under 3 different conditions.
1) With the Neon Light
2) With the Neon Light removed
3) With the Capacitor in open circuit condition (this is the best we could ever expect if we totally isolate the capacitor after it is charged using a set of relay contacts, etc.)

I charged the capacitor in each case using a 5.41 volt supply (just slightly higher than 4 fully charged NiMH batteries) connected to the slave flash unit for several minutes (just to have similar starting conditions).

Summary of findings :
1) The Neon light does reduce the capacitor voltage at full charge, but it's just a slight reduction (approximately 3 volts). Therefore the elimination of the Neon light does not appear to be a significant factor regarding higher failure rates of the slave flash unit.
2) 10 minutes is an inadequate refresh rate if the Neon light is not removed (flash stops working when the capacitor voltage is somewhere between 160 and 170 Volts, and this occurs at approximately 9 minutes assuming the capacitor was initially charged to 326 Vdc)
3) 10 minute refresh rate works with the Neon light removed, but the flash is not bright when nearing the 10 minute mark (this assumes the capacitor was initially charged to around 329 Vdc).
4) The Neon light goes out at around 220 volts, but the flash can still fire down to around 160 or 170 volts. When the Neon light goes out (stops conducting), the discharge rate appears to then be the same as if the Neon light had been removed. This happens at approximately 4.5 minutes.

0.47 ohm resistor in series with battery
The addition of a 0.47 ohm resistor in series with the battery during charging does reduce the final capacitor voltage, but it's insignificant if the unit is allowed to fully charge (approximately 2 volts difference). Therefore the 0.47 ohm resistor only helps to reduce inrush current, and has very little impact on final capacitor voltage when the battery is connected (charging) for a long period of time. The transistor on the input of my DF500 board is rated for 2 amps continuous, and 4 amps peak. Therefore inrush current control can become an important issue depending on the battery used.

Supply Voltage vs. Capacitor Voltage
4.0 Vdc Supply = 246 Vdc Capactior Voltage
5.0 Vdc Supply = 305 Vdc Capacitor Voltage
5.4 Vdc Supply = 329 Vdc Capacitor Voltage
5.7 Vdc Supply = 341 Vdc Capacitor Voltage

My Vivitar 2000 Capacitor is 800ufd with a voltage rating of 330 Volts. As the supply voltage (battery voltage) is raised, the capacitor voltage can exceed the capacitor voltage rating if the capacitor is allowed to fully charge (battery connected for a long period of time). Therefore when using SLA batteries (or 5 NiMH batteries) one should make sure proper charge and refresh time are selected in order to avoid exceeding the capacitor voltage rating.

The above information is just some preliminary test data I obtained this evening. I am sure there is variation from one Vivitar 2000 unit to another, but the information should help in the basic understanding of the Vivitar 2000 and our desire to use them in trail camera applications. I am concerned about controlling the inrush current on these units, and will be doing additional peak current readings under various conditions to better understand what should be done to prevent slave flash unit failures.

I will also try and follow up with similar data for the Vivitar 2800 slave unit.

I want to note that I measured voltages at only 1 minute time intervals, and only had my fluke digital volt meter connected for about 1 second each minute to avoid skewing of the data due to the non infinite input resistance of the volt meter. This might seem insignificant, but it can become a factor when dealing with the small capacitor leakage currents we are dealing with.

Don Kirk

This post has been edited by dkirk: Aug 12 2006, 01:39 AM

Attached File(s)

 Vivitar_2000_Capacitor_Discharge.pdf ( 40.33K ) Number of downloads: 23

 

[encorepistol]

I've been messing with one of my 2800s also and have removed the lamp on it. It now ill charge upand drain off verry slowly so far not getting below a usable voltage. I just played with it late last night and didn't get to do it long enough but it seems for some reason to hold the cap charge longer than I originally expected. A 2800 when new and not tampered with will charge up over 300 volts ( at least mine do) and drain the cap off at a high rate. I'm gonna play with it some more also and see what I find.

[Dakota]

Thanks for sharing your results. Try doing the low power mods and add that to your graph. Just make sure you stop the initial charge at ~330V for a similar test. I've done similar tests with the 30157 board in the past but never the DF500. You should find a fairly quick drop down to the 300V level and then it starts to level off only needing a 20-30 min refresh to stay over 250V.

Thanks,

Mike

[tree sight]

How much more drain on the power supply would it be on the slave batteries between a refresh every 20 min. for 10 seconds and one every 10 min. for 5 seconds assuming the slave could charge up in as little as 5 seconds? Any guesses?

tree sight

[edshere]

dkirk,
Finally somebody else agrees that a cap will drain very slow and eventually taper flat at a fairly high voltage if you completely isolate the cap. The flash board that i use doesn't have to refresh at all. Simply charge once a day when the photo resistor says its dusk. Take your vivatar charge it up, take the cap off. After 12 hours you should have around 280 volts, at least with my 400uF cap. The key to battery life is to isolate the cap.

Good Work.

[dkirk]

(Just moved the information below to a new posting.)

I just went back and tested the Vivitar 2000 "Low Power Mod", and amazingly it just about matches the performance of having the capacitor totally isolated from the circuit (updated graph attached).

The “Low Power Mod” involves removing a 10 K ohm resistor that feeds the “bounce back circuit” and associated zener diode, and this reduces the load on the capacitor which therefore reduces the rate at which the capacitor discharges. The “Low Power Mod” also involves removal of the Neon lamp, or the 1 Meg Ohm resistor that is in series with the Neon lamp.

The “Low Power Mod” did result in the capacitor being charged up to a maximum voltage just slightly higher than the “non modified Vivitar 2000” (approximately 6 volts higher), but this is not a significant amount (charged up to 332 Volts using a 5.41 volt power supply).

Elimination of the “bounce back circuit” causes the slave to discharge down to around 65 volts after the slave is triggered (similar to running the slave in “manual” mode), and this causes the slave to encounter high inrush current when recharging after each trigger event.

The main concern I now have is the inrush current. The inrush current exceeds 2 amps when using 4 NiMH batteries when charging a totally discharged unit, and this exceeds the 2 amp continuous current rating of the Vivitar 2000 inverter transistor. Including a 0.47 ohm resistor (2 watts or larger) in series with the battery results in a peak in rush current of 1.889 amps which is a reasonable value. The high inrush current may also be hard on the inverter high voltage transformer, so limiting the current is a wise thing to do.

Based on the above data, I will use the “Low Power Mod”, but will also include a 0.47ohm resistor in series with my battery. The addition of the 0.47 ohm resistor will slow down the rate of charge, so slave charge time will have to be adjusted accordingly.

It would be nice to slightly reduce the voltage that we charge the capacitor to since we are currently charging it close to its maximum rated value. Reducing the capacitor voltage slightly will also help to lengthen the life of the strobe tube. An alternative solution would be to change the capacitor to a higher voltage rated capacitor with possibly slightly lower capacitance.

Hope everyone interested in the Vivitar 2000 flash has found this information helpful.
Don Kirk

This post has been edited by dkirk: Jul 30 2006, 03:15 PM

Attached File(s)

 Vivitar_2000_Capacitor_Discharge_Rev1.pdf ( 44.87K ) Number of downloads: 9