ARC 4+

Arc 4+, retail $185.00 (WWW.ARCFLASHLIGHT.COM)
Manufactured by Arc Flashlight, LLC (WWW.ARCFLASHLIGHT.COM)
Last updated 04-25-12

IMPORTANT! Effective 09-22-04, this product is no longer being made, but here is information on it anyway.

This is the latest incarnation of the Arc LS flashlight, known as the Arc 4.
This flashlight features a microcontroller to allow it to have many modes, a very nice, bright 1.2 watt LS (Luxeon Star) LED at the bottom of a smooth reflector, and a rubber covered pushbutton on the tailcap.


The Arc 4+ has a number of different modes available, which are explained below:
(Caution: This is a long read; if you have to go pee pee or get a drink out of the fridge or something, go do that now.)

“Constant On” Activation
Depress the button briefly (about 1/4 second or less) for constant light. To turn the light off, press the button briefly again.

Momentary Activation
Press the button for a longer period of time (more than about 1/4 second) for momentary light. To turn the light off, release the button.

Note: For momentary use, the light will only stay on for as long as the button is pressed. This feature was designed with typical momentary use in mind. For signaling, please see, Tactical Modes.

Brightness Levels
With the light on (Constant On), briefly press the button twice. The light will then change to the secondary brightness level. With each double press, the light will toggle back and forth between the primary and secondary levels.

Full Power
While the light is on (Constant On), press and hold the button to activate the full power level. This function is momentary. Releasing the button returns the light to the previous level.

Note: This function is limited by LED temperature and battery capacity to a maximum operational period typically measured in seconds. If the button is held for longer than that period, the light will override the user input and return to the previous brightness level. This is done to protect the LED from overheating.

Changing the Settings

Setting the Primary/Secondary Brightness Levels
Select the brightness level you wish to change (see Brightness Levels) and then turn the light off. While the light is off, press the button briefly five times. From here, you can perform the following:
1) briefly press the button to move to the next brightness.
2) briefly press the button twice to reverse direction and move to the next brightness.
3) press and hold the button until light stops flashing to set the brightness level to this brightness and exit the brightness setting mode.
4) If you fail to press the button for a 10 second period or fail to hold the button until the light stops flashing, the light will signal an error (brighter, dimmer, brighter, dimmer, ...) and exit the brightness setting mode without changing the brightness level.

Note: This selection process only applies to the setting (Primary/Secondary) that the light was in before you entered this menu.

If you have “Force Primary” enabled, the brightness setting menu still only sets the last user selected brightness.

Changes made to the brightness settings are retained in the event of a power interruption.

Settings Menu
The Settings Menu is used to turn on and off features of your light. Each feature will be covered separately, but the basics of changing a feature are common to all features.

You enter the Settings Menu by press the button briefly ten times while your light is off. Each feature has a unique flash sequence that identifies it and a well known position in the menu. Briefly press the button to sequence through the features. Briefly press the button twice to reverse the sequence. Note that the menu wraps around from the first item to the last and vice versa.

When you have selected the desired feature, press and hold the switch. Pressing the switch starts the set flash sequence (On, Off, On, Off, ...) that lasts for 2 seconds. When the flash sequence stops and your light turns off, you may release the switch. Note that when setting the SOS signal, your light does not turn off but instead, immediately begins flashing the SOS signal.

If you do not push the button for 10 seconds or if you do not hold the button down until the set flash sequence finishes, your light will exit the Settings Menu without changing the feature setting and displays the error flash sequence (brighter, dimmer, brighter, dimmer, ...).

The choices are:

1. Switch lock
2. SOS
3. Semi-Momentary Tactical mode 1
4. Pure-Momentary Tactical mode 2
5. Force Primary
6. Locator Flash
7. RFS (Ready For Service)

Switch Lock
The switch lock feature locks your light in the off setting so it cannot come on accidentally. If the switch is pressed while your light has the switch locked, your light flashes twice and then turns off. Note that in semi-momentary tactical mode, your light does not flash but remains off.

To release the switch lock, triple-click the switch. You can also release the switch lock by resetting your light.

The switch lock feature is the first menu item and identified in the Settings Menu by two short flashes.

The SOS feature flashes the international emergency SOS signal. The SOS signal complies with 46CFR161.013-7 for signal timing but your light is not a Coast Guard approved emergency signal.

To stop the SOS signal, turn your light off. You can also stop the SOS signal by resetting your light.

The SOS signal feature is the second menu item and identified in the Settings Menu by the SOS signal.

Semi-momentary Tactical Mode 1
The semi-momentary tactical mode changes how your light operates when it is off. A single click acts like a press and only turns your light on while the switch is pushed. A double-click is used to latch your light on. Also, when the switch is locked, there is no visible switch lock indication - your light remains completely dark when the button is pressed.

The semi-momentary tactical mode feature is a toggle setting. Setting it once turns it on while setting it twice turns it off. The setting is remembered across resets. The default setting is off.

The semi-momentary tactical mode feature is the third menu item and identified in the Settings Menu by a short flash followed by a long flash.

Pure-momentary Tactical Mode 2
The pure-momentary tactical mode provides a pure momentary mode of operation. All switch pushes (clicks and presses) are momentary. In pure-momentary tactical mode, it is not possible to latch your light on or access the menus.

To return to the previous mode (normal mode or semi-momentary tactical mode), you must reset your light.

The pure-momentary tactical mode feature is the forth menu item and identified in the Settings Menu by two short flashes followed by a long flash.

Force Primary
The force primary feature forces your light to always turn on to the primary setting. To get to the secondary setting while this feature is on, you must latch your light on and toggle to the secondary setting.

The force primary feature is a toggle setting. Setting it once turns it on while setting it twice turns it off. The setting is remembered across resets. The default setting is off.

The force primary feature is the fifth menu item and identified in the Setting Menu by a long flash.

Locator Flash
The locator flash feature flashes your light about every 3 seconds. This allows your light to be found in the dark.

The locator flash feature is a toggle setting. Setting it once turns it on while setting it twice turns it off. You can also turn off the locator flash feature by resetting your light.

The locator flash feature is the sixth menu item and identified in the Settings Menu by a short flash.

The ready-for-service feature sequences through the brighter settings when the batteries are changed. The sequence goes from dimmer to brighter. If the sequence is smooth, the battery is correctly inserted and usable. If the sequence blinks one or more times, the battery should be replaced. If no light is produced, the battery is completely dead or improperly installed.

The ready-for-service feature is a toggle setting. Setting it once turns it on while setting it twice turns it off. The setting is remembered across resets. The default setting is On.

The ready-for-service feature is the seventh menu item and identified in the Settings Menu by the ready-for-service light sequence.

Resetting Your Light
There are normally no conditions under which you will need to reset your light. However, if you should get your light into a state you cannot figure out how to get out of (or you need to turn off pure momentary tactical mode 1), resetting your light is the way to get back to a functioning state - i.e., generating light when the button is pushed. After a reset, you may still want/need to change the non-resettable features (brightness levels assigned to primary and secondary settings, semi-momentary mode, force primary and ready-for-service) to a better setting.

To reset your light, open the battery compartment, remove the battery, wait for 120 seconds, replace the battery and close the battery compartment.

The LS4 has several automatic modes:

Low Battery Indication
When your light's battery is close to being used up, the battery will not be able to supply enough power to run your light at full brightness. As a result, your light will blink - that is, momentarily turn off and then turn back on at the next lower brightness, repeating as needed to find a brightness setting that the battery can handle. When the dimmest setting is reached, the momentary offs will increase in frequency as the last remaining power in the battery is used up. Turning off your light and turning it back on resets your light back to the selected brightness. Please replace the battery before the lowest setting is reached.

The same behavior can also occur if the battery contacts are dirty. Gently wiping the battery contacts with a clean dry cloth is normally sufficient to remove dirt. If in doubt, please replace the battery.

High Temperature Indication
Your light can get quite warm on the higher settings. If you hold on to your light with a bare hand during operation, your body will conduct away any excess heat and prevent your light from getting too hot. However, if your light is sitting on a table or being held with a gloved hand, the excess heat is not easily conducted away and your light can get hot. Before your light gets dangerously hot, a thermal sensor detects the increasing temperature and reduces the brightness setting until your light cools down. Your light's temperature is regulated so that you can always pick it up safely.

Rechargeable Battery Protect
The LS4 has routines for detecting when a rechargeable battery is being used. This is important because rechargeable cells can be damaged if they are discharged below a certain voltage (this varies with chemistry). The LS4 is capable of detecting some NiMH, Nicad and Li-Ion chemistries. The LS4 will then shut off when the battery reaches that voltage (accounting for cell multiples). This shut off can be overridden for emergency light but damage will likely occur to your battery. To override, simply turn the light on again and this time it will stay on until the cell incapable of generating sufficient voltage.

The cut off for NiMH and Nicad is 0.8 volts/cell. The LS4 is designed to work with two of these type cells in series only (1.6v cutoff). The cutoff for Li-Ion is 3 volts per cell and the LS4 is designed for one Li-Ion cell only.

We recommend the following if you are using rechargeables:

- Use Nickel Metal Hydride (NiMh) or Lithium Ion (Li-Ion) if possible
- Change the battery at the first sign of a low battery
- Only used cells that are approved for consumer use
- Follow all precautions for those batteries!
- Avoid/Discontinue the use of any cell that leaks. Damage to the LS4 caused by leaking batteries is not covered under the Arc warranty.

If all this **** cornfuses you, please visit this thread on Candlepower Forums (with some pictures that may be helpful) for a "quick guide" on how to operate your Arc 4.

Update 01-05-05: I was given permission to post these two instructional graphics on this web page:

To change the battery in your Arc 4+, unscrew and remove the bezel (head); the seam is about halfway down the barrel of the flashlight. Tip the barrel into your hand, and allow the old CR123A cell to come out. Dispose of or recycle it as you see fit.

Insert a new CR123A cell in the barrel, flat (-) negative end first (so the button (+) positive end is visible), and screw the bezel firmly back on.

The flashlight will come on very dimly for several seconds, then ramp up to full power and then go out. This is the RFS (Ready For Service) function, and it's perfectly normal for the flashlight to do this when you install a good battery in it.

Picture of the business-end of the Arc 4+, showing the reflector instead of an acrylic optic.

The Arc 4+ is a very small and durable instrument that should provide you with years of service, even if you don't take care of it all that well. But you'll want to take care of it, once you see how well it's built.

The only weak link I can see is that rubber switch cover, but you'd probably have to take a knife or a razor blade to it in order to hack it up.

The lamp is what I believe is a Luxeon Star High Dome white 1.2 watt LED, with a smooth reflector to capture the light from the LED and focus it into a beam. The beam is a pure white color, with no blue, yellow, or "rotten cat urine green" visible anywhere in it.
If all Luxeon Star LEDs were this way, the flashlight market would be all over them like flies to a pile of {vulgar term for feces}. But they aren't, so there are relatively few to go around. Arc selects the whitest and brighest LEDs of the whole lot, and that's what winds up in the Arc 4+ flashlights.

The Arc 4+ uses a cobalt-gold positive (+) battery contact, so intermittents are a thing of the past.

The beam that shoots out of the Arc 4+ comprises of a circular hotspot, surrounded by a dim circular corona. This is quite normal for the Luxeon Star high-dome LED and a smooth reflector, so no worries there.

The tailcap switch is easy and comfortable to use. You can just pick the flashlight up off whatever you put it on, wrap your fist around it, and push the switch with your thumb. You can use your forefinger too, but I think just holding the Arc 4+ in your fist and using your thumb to manipulate the switch is more comfortable.

The outer portions of the Arc 4+ are covered in a HA-III (Hard Anodized type 3) finish, so it will be tough and long-wearing. The HA-III coating is very durable, so pieces of it shouldn't flake off very easily at all.

I tried to cut through the flashlight with the blade of a Swiss army knife, and was not successful.
Would I really try to cut up a perfectly good flashlight
You bet your sugar-covered toilet muscle I would, if it's in the name of science.

The unit comes with a battery and a bezel-up clip, so you can clip it onto your clothing or in a pocket or attach a lanyard of your choise to the clip. A lanyard isn't included, so if you want to use one, you'll have to buy it elsewhere.

There is a transparent disc of plastic protecting the Arc4's lens; you may either keep it there or remove it if desired. It can be removed with a fingernail; you don't need tools of any kind to do this.

Beam photograph at ~12".
Measures 310,000mcd on high, and 386,000mcd on overdrive.
Additional measurements of the light's other modes forthcoming...patience, please.

IMPORTANT: These measurements are of a "second"; "firsts" are known to be brighter.
Please do not base your purchase decision on these mcd readings alone.

Spectrographic plot
Spectrographic analysis of the LED in this flashlight.

Spectrographic plot
Same as above; newer spectrometer software & settings used.

Spectrographic plot
Spectrographic analysis of the LED in this flashlight (low mode); yet newer spectrometer software settings used.

Spectrographic plot
Spectrographic analysis of the LED in this flashlight (low mode); spectrometer's response narrowed to a band between 430nm and 480nm to pinpoint native emission peak wavelength, which is 447.573nm.

Spectrographic plot
Spectrographic analysis of the LED in this flashlight (high mode); yet newer spectrometer software settings used.

Spectrographic plot
Spectrographic analysis of the LED in this flashlight (high mode); spectrometer's response narrowed to a band between 430nm and 480nm to pinpoint native emission peak wavelength, which is 442.693nm.

USB2000 spectrometer graciously donated by P.L.

ProMetric analysis
Beam cross-sectional analysis.
Image made using the ProMetric System by Radiant Imaging.

Test unit was purchased on ebay as a "second" a few days ago from a Candlepower Forums member, and was received on the afternoon of 03-17-04.
The specific listing I purchased it from is right here, but will no longer display after 06-14-04.

The warranty is lifetime on all Arc "firsts", and 15 days return policy on "seconds".

Because this is a "second", it will not be rated like the other Arc products are. If or when I do get a "first", I don't anticipate giving it any less than 4 1/2 stars.

UPDATE: 07-09-04
You can obtain a set of hex head screws right here if you wish to remove the pocket clip and fill the two holes it will leave. You can also get an 0.050" hex wrench for $1 along with the screws if you need it to install/remove these screws.

UPDATE: 07-17-04
A user of Candlepower Forums took his Arc4+ to an underwater depth of 46 feet, and it did not leak or malfunction. Although the Arc4 is rated as being submersible to 100 feet, this was a real-world test - and the test was successful.

The same user later posted the following:

Ok I took it out this morning again. The light self activates at 66' and then will not turn off until 37'. If the light is activated below 50' the light will stay on until 37' also. But the switch works fine to 49'. The max depth for todays dive was 70' and it stayed completely dry.

UPDATE: 01-08-05
An Arc 4 "trainer" in Javascript is available right here.

Trainer was used with permission; thank you!!!

UPDATE: 01-09-05
Henry of HDS Systems has given me permission to post the Arc 4 Users Guide (PDF documentation) and the Product Description on this web page.



    MANUFACTURER: Arc Flashlight LLC
    PRODUCT TYPE: Small handheld flashlight
    LAMP TYPE: White Luxeon Star LED
    No. OF LAMPS: 1
    BEAM TYPE: Central hotspot with softer corona
    SWITCH TYPE: Rubber covered digitised pushbutton on tail
    BEZEL: Acrylic A/R window protects LED and reflector
    BATTERY: 1x CR123A cell
    CURRENT CONSUMPTION: Unknown as of yet
    SUBMERSIBLE: Yes, to 100 feet
    ACCESSORIES: CR123A cell
    WARRANTY: N/A (company has gone out of business)


    (Product is a "second", and will not be assigned a rating for that reason.)


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