mobile | classic
Dataweek Electronics & Communications Technology Magazine

Follow us on:
Follow us on Facebook Share via Twitter Share via LinkedIn


Electronics Buyers' Guide

Electronics Manufacturing & Production Handbook 2019


Ultra-capacitors help solve power problems in professional cameras
5 June 2002, Power Electronics / Power Management

The high-end model in the Rollei camera range was far ahead of the technology of the time when it was launched, but still required a rechargeable battery. Today, state-of-the-art Ultra-Caps from Epcos open up a solution that was not feasible in the '80s - a capacitively-buffered circuit that always delivers the right amount of power, even in combination with batteries.

When Rollei developed its concept for a new medium-format camera in 1976, one of the key ideas was to implement a diaphragm shutter directly controlled by an electronic circuit. A shutter of this kind consists of five ultra-thin blades which must be moved as quickly as possible. The solution was a moving coil motor acting directly on a ring, which then rapidly turns the blades into the optical beam path. Although the blades only weigh about a tenth of a gram, forces of some 15 N must be momentarily applied to obtain the fast shutter speeds required. At the fastest speed of 1/1000 s, the shutter must open and close within in about 300 µs.

Rollei developed a special moving coil motor to generate these forces. Its operating principle is comparable to that of a loudspeaker coil. The coil was controlled by a bridge circuit, which had to drive current pulses of about 8 A at 9 V for 20 ms. As space inside the camera was limited, this could only be done with specially selected transistors. Rollei used a pack of eight rechargeable NiCd batteries with overall dimensions of 30 x 35 x 70 mm as the current source because no other source could supply the pulse power required.

Modernising a classic

Features like the electronically-controlled high-speed shutter made this professional camera from Rollei look excitingly modern in comparison with competitor models. Today, 25 years after its introduction, its successors can stand up to any comparison. Over the years, the medium-format camera - as represented by Rollei's System 6000 today - has been evolving all the time. The uncommitted logic array circuits of yesterday have given way to state-of-the-art microcontrollers, while driver transistors in TO-36 packages have been replaced by SOT 223 types. Many Rollei users had long been wanting to replace the power pack by a stationary power supply unit fed from the AC line, or by standard batteries for emergency use when the rechargeables were flat. But this was not feasible at the time because the capacitors needed to supply the camera with 10 A for about 10 ms were too large for the battery pack.

To supply 10 A for 20 ms with a maximum voltage drop of 2 V at the same time, capacitors rated at more than 100 000 µF would be needed. This would not be feasible with conventional aluminium electrolytic capacitors because of space restrictions. A stationary power supply unit fed from the AC line would require a connecting cable more than 2 m long to give the photographer enough freedom to move, not to mention large cross-sections and bulky connectors.

The use of capacitors with high ratings, such as Gold-Caps, was considered but then rejected because their internal resistance invariably proved too high. Not until Epcos launched UltraCaps did it became possible to house a capacitively buffered circuit inside the battery pack (Figure 1).

Figure 1. UltraCaps support fast shutter release
Figure 1. UltraCaps support fast shutter release

UltraCaps for more mobility

The key components of this circuit are six UltraCaps connected in series and rated at 8 Farad/2,3 V each. All six fit inside the power interface. Via an input regulator (low drop, 12 V, 1 A), this circuit is charged to a maximum of 12 V from an external power source, which may even be a car battery. The connecting cable needs only a small cross-section and can thus remain flexible, as currents of no more than 1 A flow through it.

Because the series circuit also represents a sixfold internal resistance, a normal 10 µF electrolytic capacitor is connected in parallel with it to counteract the first voltage dip. The voltage is then stepped down from 12 V to about 9 V/10 A by another low-drop control circuit to power the camera. Once charged, this capacitor circuit permits the camera to be triggered several times in rapid succession. Standby operation is also possible as long as the external source supplies a current higher than the standby current of the camera electronics. The camera can also be supplied from practically any source, including ordinary, nonrechargeable batteries, which was not feasible before due to the high currents required.

The directly-controlled shutter remains a key feature in the Rollei product spectrum. For studio use, the shutter is combined with a lens control unit (figure 2), which previously had to be powered by the NiCd battery pack. This control unit can now be powered from the AC line and batteries. Here the circuit containing the UltraCaps and the electrolytic capacitor ensures that the required current of 10 A is always available.

Figure 2. UltraCaps also offer more freedom of movement for Rollei’s lens controller
Figure 2. UltraCaps also offer more freedom of movement for Rollei’s lens controller


UltraCaps offer numerous advantages for portable systems powered by rechargeable batteries: the internal resistance of the power supply unit is dramatically reduced; short, fast pulse sequences can be triggered even if current sources have high internal resistance; rapid recharging of UltraCaps permits fast pulse sequences; the operating life of the rechargeable batteries is prolonged; current sources with higher internal resistance can be used instead of rechargeable batteries with extremely low resistance; thanks to the high capacitance of UltraCaps (up to 3,6 kF per cell), the overall system remains compact.

Supplied By: Electrocomp
Tel: +27 11 458 9000
Fax: +27 11 458 9034/5
  Share on Facebook Share via Twitter Share via LinkedIn    

Further reading:

  • Rugged DC-DC converters
    28 August 2019, Vepac Electronics, Power Electronics / Power Management
    XP Power introduced two new series of wide input-range chassis- and DIN-rail mount DC-DC converters that offer simple and rapid installation into a wide variety of industrial and ITE applications. The ...
  • Power controller for smart home appliances
    28 August 2019, RF Design, Power Electronics / Power Management
    Qorvo has introduced a new intelligent power control solution for reducing energy consumption, bulk, weight and noise in smart home appliances, AC-powered fans and compressors. This mixed-signal system-in-package ...
  • UPS battery configuration made easy
    28 August 2019, Forbatt SA, Power Electronics / Power Management
    Determining the UPS (uninterruptible power supply) battery configuration using a formula can be quite complicated and, since many users are not very familiar with it, a more simplified method can be used ...
  • GNSS boards for dead-reckoning
    28 August 2019, Electrocomp, Telecoms, Datacoms, Wireless, IoT
    The Locosys RTK-4671-SHDR/MHDR is a high-precision GNSS RTK (global navigation satellite system real-time kinematics) solution targeting the smart driving and lane-level navigation markets. The newly ...
  • Rugged PFC capacitors
    28 August 2019, Electrocomp, Passive Components
    TDK’s DeltaCap X Black Premium is a new series of Epcos MKD capacitors for power factor correction (PFC). With rated voltages of between 440 V a.c. and 850 V a.c., the capacitors with an internal delta ...
  • Bidirectional laboratory power supply
    28 August 2019, Vepac Electronics, Power Electronics / Power Management
    EA Elektro-Automatik’s new 30 kW EA-PSB 10000 is a bidirectional power supply with a working efficiency of up to 96%, both as a source and as a drain with energy feedback. The device can be switched from ...
  • 3 Watt DC-DC converters
    28 August 2019, Avnet South Africa, Power Electronics / Power Management
    Aimtec has introduced three new series of switching regulators – the AMSRB1-78JZ, AMSRL1-78JZ and AMSRL-78JZ – all meeting the EN62368 standard and suitable for IoT (Internet of Things) applications. The ...
  • Isolated PFC module
    28 August 2019, Conical Technologies, Power Electronics / Power Management
    SynQor has added a new isolated PFC (power factor correction) module to its AeroQor range of products for the airborne electronics market. Featuring highly efficient active power factor correction, the ...
  • DC-DC converter for DIN-rail mounting
    28 August 2019, Vepac Electronics, Power Electronics / Power Management
    MTM Power is offering the HSD series of primary switched DIN-rail modules with DC input voltage. The devices offer an input voltage range of 20 - 72 V d.c. and allow efficient solutions for different ...
  • Power inductors for LED headlights
    28 August 2019, Electrocomp, Passive Components
    TDK has expanded its lineup of metal core power inductors with the new SPM-VT series that is designed especially for the high thermal and current demands of automotive LED headlights. These wire-wound ...
  • DC UPS for DIN-rail mounting
    31 July 2019, Vepac Electronics, Power Electronics / Power Management
    The Effecta DCH series power supplies with UPS function are suitable for a variety of applications, and their robust IP 20 housing is applicable for all DIN-rail applications. With its power boost mode, ...
  • Ferrite magnetic design tool
    26 June 2019, Electrocomp, Passive Components
    The MDT software from TDK allows application-related parameters to be calculated for all available Epcos ferrite cores and/or materials. It provides access to digitalised material data including their ...

Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronics Buyers’ Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Terms & conditions of use, including privacy policy
PAIA Manual


    Classic | Mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.