Review, Teardown: Sevenoak SK-EBH01 Electronic Ball Head

Time lapses have a very interesting effect in the way they compress time, allowing the viewer to observe things that may happen very slowly over a long time which would be impractical to witness in real-time, or to appreciate the result of many short, fast processes being built up over time in a short time frame.

An ordinary time lapse requires only a camera that can either shoot video, or still images at intervals over a long period, with the resulting footage sped up or images assembled into a video. This is easily achieved with a DSLR, suitable power source and an intervalometer remote, noting that it is a way to consume quite a few of your “limited” shutter cycles. You can do the same with a webcam, or even compact cameras running aftermarket firmware. I did this in Hong Kong on my recent trip, and it let me “relive” exactly what was happening in the busy port long-after I had left.

A static time-lapse with a fixed view-point can be interesting, but to add a little more visual flair to it, a panning time lapse could be more appropriate and engaging. I tried my hands out at this using a clockwork style gadget which uses repurposed kitchen-timer parts in my trip to Minnamurra Rainforest and to Auburn Botanic Gardens, but sadly, the unit in question wasn’t able to handle the weight of a DSLR properly causing it to bind together and judder. Another limitation was the fixed 60 minutes for 360 degrees rotation rate.

As a result, I went shopping for something a little more suitable, and a little more versatile.

The Product

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The unit in question is known as a Sevenoak SK-EBH01 Electronic Ball Head, and is available from eBay for about AU$130. The name itself is a little vague, but it is basically a pan-head that is electronically controlled and actuated. At this stage, it is a unique product on the market, as I hadn’t seen any others at the time of purchasing.

When purchasing the product, you don’t get a cardboard box – instead, it comes packed in a miniature “roadies” case for protection. Sevenoak is a brand you might not have heard of, but they are a Chinese company that makes quite a few photography-related accessories. As to the quality of the accessories, I can’t really vouch for them as this is my first.

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To verify authenticity, there is a scratch-off label at the top, however, since it;s mounted on the textured plastic, scratching it a little too hard will cause the printing to be destroyed and the rear of the label to separate. This causes an issue for scanning the code – but luckily, I did some Photoshop enhancing of my label and it was “recoverable”. It was scanned out as genuine.

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20150709-1817-0540This unit was sent to me by DHL Express Shipping from Hong Kong, and sadly, it was damaged at an inspection, with scored outer plastic packing visible above and to the left. This was relatively minor damage, but is the second damaged DHL shipment I received in a row.

This may be because the shipment contained Li-Poly cells but wasn’t properly documented.

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The box comes complete with a latch and carry handle, which isn’t strictly necessary, and more for aesthetic value. I suppose it’s not a bad carry case either, but the aluminium stripping around the edge doesn’t look very well formed. Lets open it and look inside!

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20150709-1818-0544 20150709-1820-0545Inside the case, there is a power adapter for charging the unit, a fold-out leaflet manual (single page, colour, with English) and the “electronic ball head” unit itself.

The power supply on my unit is an EU model, and is rated for a 12v 1A DC output to a regular 2.1mm style barrel connector. I had to rummage and find an adapter to use it.

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Rather disappointing, upon removing the unit from the casing, I found it had a cracked power switch that falls off as soon as it’s used, and slight damage to one of the buttons on the front of the unit. As a result, the seller was contacted and a partial refund was accepted as compensation, with an official case lodged with DHL.

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Anyway, the main unit is basically a painted metal cylinder, a little larger than a soft-drink can, and about one-third the height. On the turntable is a scale, marked in 5-degree increments. On the bottom body, we see LED indicators indicating direction (on = clockwise, off = anti-clockwise), rotation angle (15, 30, 45, 60, 90, 180, 360 degrees) and rotation time (5, 15, 30, 60 minutes). A slide power switch is provided to turn the unit on and off. Three push buttons are used to set the duration (i.e. angle), rotation time and direction (by pressing both Duration and R.T buttons). A dedicated button is used for start and stop.

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Further around the unit, there is a 2.1mm socket for the charger input, and a bi-colour LED to indicate charging status – red for charging, green for complete.

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20150709-1823-0552The top turntable is mostly covered with non-slip patterned rubber, with a tripod screw fixed in place in the centre for attachment to a camera. The underside is mostly painted metal, slightly recessed, with four screws holding the bottom plate in place. A tripod thread is placed in the centre for attachment to a tripod.

The unit itself isn’t light, weighing in at 458 grams, which is a consideration for travellers. It claims to support up to 1kg of weight depending on mounting orientation.

Teardown

I have a new toy, so what to do with it? Tear it down of course! This one is an easy one to get into, as it was built only with four Philips screws in the base. Removing them allows you to remove the bottom plate and get a good look inside.

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Internally, starting from the bottom, we can see two lithium polymer batteries with their own protection boards, wired in series to form a 7.4v battery. These cells are padded with foam and wedged into place to prevent movement. The makers of the cells were not ascertained.

The centre of the unit is dominated by a 35BYJ412 small high-torque stepper motor. This is a very generic unit, which is 4-phase, and 3.75 degree step angle, intended for use in louver control for air conditioners and fans. This unit can be had for US$13.50.

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Looking more closely at the PCB, we can see that the power is being supplied by an National Semiconductor LM2577S Simple Switcher Step-Up Voltage Regulator, producing 12v for the stepper motor from the 7.4v pack.

The stepper motor itself is being driven by a THB 6128 PWM stepping motor driver. Battery charging is handled by a Consonance CN3702 PWM switch-mode 2-cell battery charger. Unfortunately, it seems there is no cell balancing feature, so there is a possibility of premature battery failure due to cell mismatch, however, as each cell has it’s own protection board, it should not result in safety issues. This drives an STM9435 P-channel MOSFET.

The intelligence behind the product lies in the Microchip PIC16F1937 8-bit microcontroller, seen with its own clock crystal next to it.

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The other side of the board shows the front panel buttons, four-wire connection to the motor, two-wire connection to the battery, inductors and capacitors for the switch-mode charger and voltage regulator, the bi-colour LED and a ribbon cable to the LED array further up in the body. There is also a surface mount AMS1117 5v linear regulator for the PIC.

According to the PCB itself, the board was designed 11th August 2014, and this board was fabricated in Week 4 of 2015, making this a very recent product. The lettering EBH01-M1 suggests this may be the first revision of the first model of this product they’ve designed. That shows, as the underside has one “greenwire” trace, which suggests there may be a subtle routing issue with the PCB itself.

I didn’t continue deconstructing the unit from here, as it was mostly mechanical, but it might have been nice to get a better view of how the motor was coupled to the turntable … maybe next time. However, it doesn’t look like there are any exotic or special components, most of them are very “commodity” and it would probably be worth $40-50 to make from parts.

User Impressions

The first thing you realize after holding one of these is how this improves the flexibility over the cheaper, and more common, clockwork type mechanisms. They generally are fixed speed clock-works with no chance to change your rotation rate. They are fixed at 60 minute (6 degrees per minute) or 120 minute (3 degrees per minute). You can change the angle only, by reducing how far you “wind up” the clockwork. With the Sevenoak SK-EBH01, it’s much easier as all the settings are controlled electronically and are relatively intuitive. Having this array of angles and times, you actually have many more rotation rates to play with, so much so that I made a table of them.

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As you can see, there are 15 unique rates of rotation all up, however, the matrix of settings only provides you at most 28 unique settings. So, while there is flexibility, you are limited by the increments of angles, and times. This is shaded in green in the time-for-angle-at-a-given-rate table on the right. If you were willing to attend the unit and push the start button every time the unit stopped, then you can also have the purple shaded cells with an integer number of button pushes. The white cells can also be achieved, although will involve manually stopping the rotation when it reaches your goal.

The unit feels solid and weighty, and its weight may be of concern to travellers especially as it contains lithium polymer cells which may be restricted from travelling in checked-in baggage. Despite the weight, it seems the plastic buttons may be a little less durable than the metal body itself.

The unit itself is fairly simple to operate, but the LED feedback can be hard to read in full sunlight conditions. The LEDs are solid when setting, and the time LED blinks when the unit is running. No progress feedback is given, aside from reading the scale on the turntable. There is also a low battery indication by a different sort of blinking of the duration indicator, but no battery remaining indication, although it should last 8 or so hours of usage. Charging is similarly instrumented with either “charging” or “done” indications.

The scale itself did seem somewhat strange, as when mounting the unit onto the camera, the tripod screw is not adjustable separately to the camera. When twisted onto the camera, the lens was not aligned to the 180 degree mark, meaning the unit was always “at a skew”, making controlling the unit and not being in the view of the lens potentially challenging, and checking the shot progress relatively difficult. There are also no rubber feet on the bottom of the unit, if you wish to use it with a lighter camera, sans tripod, as the bottom plate itself is slightly recessed from the edge, making it a little too easy to move accidentally when on smooth surfaces.

Initially testing the unit, I did have some concerns, as the turntable is not rigidly fixed in place. It feels like it may be connected by a toothed belt or similar, as it has about 3 degrees of play to it, which could make for jerky pans should there be significant wind-load or varying weight loads. It has more than sufficient torque, although if the platform is artificially stalled, the torque builds up like tensioning a rubber band, and when released, the platform “jumps” into the correct position. This may not be a desirable property to have.

Further testing showed that the motor drive did emit audible noise. At high rotation rates, it made a sound similar to a clockwork mechanism, going “tick-tick-tick-tick” but with a more “whiney” note to it. At slow speeds, the unit had a hissy, whiney character to it. The audible noise was relatively quiet, but audible to me while shooting and probably wouldn’t be welcome in videos.

Given this is microcontroller controlled, there is no reason why it couldn’t have been designed more flexibly, say with a 7-segment display and LEDs to input precise step angles and times into the unit. This could probably even give progress feedback on the shot and charging instead of trying to work out the time or reading the scale marked on the turn-table. Maybe they could adjust the markings on the outer ring to compensate for different cameras and their orientation when screwed onto the platform. With some additional work, they may have been able to incorporate a Bluetooth module into it so that it can be programmed to do more complex drive patterns – maybe variable-speed/ramp-speed and automatic direction reversal, or multiple rotations.

Another missed opportunity was to incorporate a zero angle sensor to automatically return the turntable back to the “home” position after use. Instead, we are instructed to set it to the 5 minutes/360 degrees setting and run the turntable until it gets to zero to reset the unit, with a warning that forcing the turntable around can damage the unit. This gets tedious after a while, and the scale itself is of limited help. There is no big issue with using it starting at an arbitrary indication, say starting at 210 degrees, as the unit will still perform its rotation as instructed.

Maybe we can look forward to another version, possibly even a competing version, that brings more advanced capabilities to the table.

Test Time Lapses

Sadly, I received the unit almost a month back, but I never had the time to test it out. The biggest hindrance was the weather, which was being atypically grey and wet at the time. As a result, the unit sat around for a bit until just this week when I had the bright idea to shoot some time-lapses at the uni (since I was going there to see my supervisors and get things done anyway).

One reason I really like using my DSLR to shoot time lapses is that I have the advantage of shooting every frame as RAW. This gives me a much better advantage when it comes to dynamic range, which I can “compress” in post processing to eek out more from the shadows and restore some of the highlights. It also means exposure setting is somewhat less critical. I performed the image processing in Adobe Lightroom, exporting TIFFs which were converted to BMP and then sucked into ffmpeg to assemble a video, which was finally encoded with Handbrake.

It is also an easy and affordable way to get high quality uncompressed 4k source material, as most DSLR’s have more than the 3840×2160 resolution required, and in fact, my frames were downscaled from cropped 6016×4000 RAW shots, thus making these somewhat “futureproofed” time lapses where every little detail is visible (forgiving the YouTube compression which smears details).

As a result, to enjoy these as best as possible, I would suggest opening the video directly in YouTube’s player, going full-screen and selecting the highest resolution your bandwidth can allow, even if it’s higher than your native screen resolution, as you will suffer less from compression artifacts. Maybe even view them at your university where there’s high speed internet … if you’re a student. All of these were uploaded in full 4k resolution.

Time Lapse #1 – UNSW Scientia Sunset on 3rd August 2015

The first time lapse was taken at the UNSW Scientia building, on the ledge, looking towards Electrical Engineering and the main walkway. The shot was planned as a 180 degree sweep in 60 minutes, beginning at 4:45pm, as sunset was at 5:17pm according to Geoscience Australia. A total of about 3000 shots were recorded.

I used my Nikon D3200, with my Samyang 8mm f/3.5 fisheye lens. Unfortunately, due to some bugs with the Nikon D3200 in fixed white balance mode driven constantly by an intervalometer at one-second intervals which it can barely keep up with, the red channel data seems to have “bursts” causing the image to tint red every few shots. This was confirmed even reviewing the RAWs on camera, and is much more evident when in shadows. Because my Samyang was a manual (non-AE) lens, I had to select one exposure time and ISO (ISO 100, f/5.6, 1/160s) and shoot the whole sequence past sunset with it and amplify the light post-process. This could be done to a few stops before noise and the sensor “manufacturing” patterning started to appear.

The area was pretty windy, and it seems there are a few “shakes” due to the wind. I had removed the camera’s strap to reduce the wind loading as much as practicable. At least, this demonstrates the ~700 gram combination of my DSLR was successfully driven by the Sevenoak SK-EBH01, and the results were promising.

Time Lapse #2 – UNSW Gate 2 Morning Peak on 5th August 2015

The second time lapse used the same gear but instead, I headed to university early one morning to get a time lapse of the buses arriving at Gate 2. The shot was started at 8:30am, with the head set to turn 90 degrees in 1 hour to capture the 9am “morning peak”. At the end of the turn, I hopped in and quickly configured it to reverse direction and turn 180 degrees in 15 minutes to create a “reversing” sweep, demonstrating the flexibility of the unit. It’s interesting to note, on the uphill direction, I counted an average of one bus every 45 seconds. That’s the morning rush of UNSW.

In all, I think the results are quite acceptable. I would have liked to shoot more time lapses, but I didn’t have the time. Who knows, maybe you’ll find future posts with videos made with the aid of the Sevenoak SK-EBH01.

Conclusion

The Sevenoak SK-EBH01 is a unique product in the market, providing configurable electronically-actuated timed panning for time lapse video and photography purposes. It seems to be physically well built aside from the buttons, and has fairly basic but intuitive controls. It is able to perform satisfactorily, although the turntable did have some play to it. It is a little pricey at AU$130, especially given the basic commercial off-the-shelf components used in its construction, and it does feel like a product whose potential is not fully realized yet. A lot more configurability could be had for very little work, and it is surprising that they didn’t pursue this path. Definitely something worth considering if you want a little more than what you get from fixed clockwork devices.

About lui_gough

I’m a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!

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5 Responses to Review, Teardown: Sevenoak SK-EBH01 Electronic Ball Head

  1. Pingback: Experiment: Circular Quay Timelapse (14 Aug 15) | Gough's Tech Zone

  2. Ashish Bhatnagar says:

    Are you experiencing jerky movement of turn table…I got this product yesterday and my timelapse is very jerky…

    • lui_gough says:

      I posted samples, but generally no issues. Only exception is in windy conditions with heavy load mainly due to play in the mechanism (maybe there’s a belt involved somewhere) which allows a little forward/backwards rocking by external forces.

      Depending on your equipment, you will need to check if it’s an issue with your intervalometer (DSLR short intervals can result in buffer overflow especially if card cannot keep up resulting in lost images and jerky output), or if it’s an issue with the format/playback.

      – Gough

      • John Tolmie says:

        Your time lapse videos do show some stepped movements which is particularly noticeable for things moving into the frame from the edge. This is not so great since the time lapses were shot with such a wide lens.The effect would be much more noticeable with a longer lens. I would be interested in more information about its mechanical design such as the reduction ratio of the gearbox. This would allow me to work out what movement for each motor step and how many steps per second for each movement rate. I noted that 15 degrees in 60 minutes is the same rate as one rotation in 24 hours. This would be the correct rate to freeze the moment of celestial bodies in the frame (with the correct orientation of the device) i.e. remove the earths rotation. This could be used for very long exposures at night but my feeling is that the mechanism is probably not smooth enough to yield good results.

        • lui_gough says:

          I agree – these units are really only intended for the amateur photographer/videographer, and they do use a stepper motor along with gearing and what feels like a belt. Even though it attempts to microstep, there is some cogging and significant amounts of backlash in the mechanism – I wouldn’t trust it for astrophotography or long exposures. I wouldn’t trust it to be accurate either. At the time I purchased it, it was the only electronic option that had variable speed that I could buy – the only other option were mechanical clockwork timers which have a tendency to get stuck.

          As to the gear ratios/step .. I can’t be sure unless I take it apart to bits. As I really don’t want to damage my own unit, and I really don’t feel the need to do it, I’ll leave this to be answered by somebody else.

          – Gough

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