BioStim universal biological stimulator system

BioStim stimulators are very popular equipments, because they are

    - Sophisticated, top-grade, professional stimulators. They meet any difficult requirements in any laboratories.

    - Despite the powerful services, they are user friendly, and easy-to-use. BioStim does not need special

       technical or computer skills, an average technician can learn its usage very quickly.

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Our method is, how we improve the features of our BioStim equipments, that we collect all the notices and feedbacks from our customers. In this way we implement the knowledge of our customers into the features of BioStim

The BioStim system must not be used in human experiments, because it has not got European permission for human applications.

The parts of the BioStim universal biological stimulator system

The BioStim system is divided into two functional parts. The time parameters are generated by the fully digital BioStim Controller, and the analogue voltage and current sources are implemented in the End-stages. The parts of the system are manufactured as independent equipments. On one hand it results a more flexible and variable system, because the similar parts (e.g. the End-stages) are compatible, and they can be changed easily. On the other hand the divided system meets the special experimental requirements much better, because the analogue End-stages can be located close to the biological objects in the shielded environment, but the digital BioStim Controller, can be placed anywhere else. BioStim Computer Interface is an alternate of the BioStim Controller in special cases. You can find detailed descriptions about each components of the BioStim system in the appropriate manuals.

The General Overview of the BioStim Universal Biological Stimulator System is downloadable.

BioStim Controller

BioStim Controller is a dual-processor system. There are two independent RISC microcontrollers built into one cage. One of them, the Repetition Cycle and Gate Controller can be used to generate the periodical repetition trigger events, or it can be used as a gate generator to enable, or disable the output pulse sequence. The other microcontroller is the Pulse Pattern Generator. It is used to generate the different output pulse sequences (as listed below).

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The accuracy of the time parameters in BioStim Controller are guaranteed by internal crystal pacers. All the programmed time parameters are stored in built-in non-volatile memories. They hold the previously used values during switched off periods. Easy programming operations are carried out in menu system, with 4-button keypads. The displays of the microcontrollers are 4 x 20, and 2 x 16 character alphanumeric models with backlight to provide good visibility.

BioStim Controller (together with one of the End-stages) can be used as a stand-alone stimulator, but both of its microcontrollers have got bi-directional digital control capabilities: Start Input, Gate Input, and Synchron Output. These TTL-compatible control bits offer a huge versatility in the different applications. BioStim Controller can be started externally (with rising edges at Start Inputs) from another equipment (for instance a PC), or it can be the master synchron generator (if the external equipments are triggered from its Synchron Outputs), as well.

BioStim Controller has got nonvolatile memories to store all parameters of the functions. If you use the equipment in a fixed application, you should program it one time only. If you switch the BioStim Controller on, it checks, which function was used last time. After it the parameters used by the actual function are checked. If the parameters have got valid values preset, the last used function will be started automatically.

The operating modes of the BioStim Controller

Programming conventions, and definition of terms in connection with the BioStim Controller

The functions are categorized in two groups. The first group contains the 'single' functions. 'Single' functions are initiated by the START event. After a START event they generate their sequence one time only (an example is Single Burst). The other category is the group of the 'repetitive' functions. They repeat their sequence periodically based on an internal crystal pacer (an example is Continual Bursts).

A subcategory of the 'single' functions is the group of the 'delayed' functions. They are the same as their appropriate 'single' equivalents, but a programmable delay is occuring at the beginning of the sequence before the first Output pulse.

START event means a keypress on START button, or a TTL rising edge appearing on Start input. The two source of Start event can be used together or independently any time (they are in logical OR relation).

You can clear all stored parameters if you press and hold F button down, while BioStim Controller is switched on. During programming actions the equipment checks the validity of the actual value. If you try to accept (with F button) a number out of range, the software will not allow it. If more than one parameters are incoherent, you will be asked to correct them.

UP and DOWN button is used to navigate in menus, and to modify parameter values up or down, respectively. F button is used to select a menu item, or accept a parameter value. Furthermore, F button is used to cancel a function if it is running. If you cancel a function with F button, you will get an access to Function Choice menu. START button is used to start the sequence of pulses, if a 'single' or a 'delayed' function is selected actually. The 'repetitive' functions can be interrupted temporarily with START button (and they can be restarted again with it).

The operating modes of the Repetition Cycle and Gate Controller in BioStim Controller equipment

Repetition Cycle:

This function can be used to generate periodical repetitive trigger events in such cases, when the BioStim Controller is the master synchron generator of the data acquisition process (in such cases, if the external data acquisition equipment, such as a PC is triggered from its Synchron Output). In this function the Synchron output of the Repetition Cycle and Gate Controller provides repetitive Start events for the Pulse Pattern Generator, on which any of the ‘single’ patterns should be selected. To use the Repetition Cycle function the Synchron Output of the Repetition Cycle and Gate Controller should be connected to the Start input of the Pulse Pattern Generator with the appropriate switch at the back side of the BioStim Controller. The repetition cycle time (Tc) can be set from 80 ms - 60 sec, with 10 ms of resolution. A wide (50 ms) Synchron pulse is generated at the beginning of every Repetition Cycles. These Synchron pulses are the synchron pulses of the whole time sequence, if the Repetition Cycle function is used, and a ‘single’ pattern is initiated on the Pulse Pattern Generator. The Repetition Cycle and Gate Controller has got its own TTL-compatible Output, which is independent from the Output of the Pulse Pattern Generator. The Output pulse of the Repetition Cycle and Gate Controller (0.1 - 24.9 milliseconds in width, with 0.1 ms of resolution) can be used for any other controlling task (for instance muting the input of the preamplifier for a programmed period before appearing, and during the stimulating pulse at the Output of the End-stage), if it would be necessary.

Gate Generator:

This function can be used to generate a programmed enabling period for the Gated Continual function of the Pulse Pattern Generator. To use the Gate Generator function the TTL-compatible Output of the Repetition Cycle and Gate Controller should be connected to the Gate Input of the Pulse Pattern Generator with an external cable at the back side of the BioStim Controller. This combination of functions can be used to produce very long bursts of pulses. The duration of the burst is defined by the Repetition Cycle and Gate Controller. The timing data of the pulses, and the pauses should be programmed at the Pulse Pattern Generator in its Gated Continual function. The gate time (Tg) can be set from 80 ms - 60 sec, with 10 ms of resolution. A wide (50 ms) Synchron pulse is generated at the beginning of every Gate periods. These synchron pulses are accessible at the Synchron Output of the Repetition Cycle and Gate Controller.

The operating modes of the Pulse Pattern Generator in BioStim Controller equipment

The actually realized 12 operating modes of the Pulse Pattern Generator in BioStim Controller are presented in this document. They have got a graphical interpretation to explain them in fine details. In a few cases there are more than one function with which a paradigm can be carried out. You should always consider, which function is the best one to your special task.

BioStim Computer Interface

There is an alternate equipment, BioStim Computer Interface in our choice to substitute the BioStim Controller in that cases, when a computer software is used to generate the sequence of the stimulating pulses. BioStim Computer Interface has got a universal connector to connect any of End-stages of Supertech, a power supply unit to supply the End-stage, and two TTL-compatible digital input connectors. Its TTL inputs are configured in logical OR function internally. The TTL standard describes the voltage, and load specifications of the inputs, and outputs of a logic system, what is supplied from 5V. Nowadays most of the microcontrollers, and logic systems use 3.3V of supply voltage internally. The inputs of the BioStim Computer Interface accept the logic levels of the 3.3V, non-standard-TTL systems correctly, with optimal noise margins, too. Basically BioStim Computer Interface realizes the DC via Control function (see later in this description) of BioStim Controller. If a sophisticated software is used, it is not necessary to install the BioStim Controller, it is enough to use the BioStim Computer Interface. The disadvantage of this arrangement is, that a fast computer, and an appropriate software is always necessary to be used. An independent, universal, stand-alone stimulator can be formed only by using of the BioStim Controller.

Universal Floating End-stage

The Universal Floating End-stage can be used either in microelectrode experiments, or in body surface applications on animals. There is a Constant Current generator, and a Constant Voltage generator built into this End-stage. The output of the End-stage can be switched between Constant Current and Constant Voltage modes on-the-fly, during the experiment. It is a very useful feature, because the first stimulating trials can be carried out in the secure Constant Voltage mode. If the experiment is qualitatively working, the End-stage can be switched immediately into Constant Current mode, where the electric charge can be defined exactly. The Constant Voltage mode has got two ranges: 10 V, and 100 V of full scale. The Constant Current mode has got two ranges: 100 µA, and 10 mA of full scale. The output amplitude in the selected range can be set using a 10-turn calibrated helical potmeter on the front panel. The nonlinearity (total amplitude error) of the End-stage is less than 5%.

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The floating output circuit of this End-stage is supplied by an internal high frequency power source. The isolation capacitance between the mains plug and the floating output is less than 10 pF. It is good enough for most of the microelectrode experiments. The output leakage current is internally trimmed to absolute zero. A special feature of this End-stage is, that it does not generate any detectable electric noise. According to this feature it can be placed close to the experimental object even in a shielded environment.

The complete User Manual of the Universal Floating End-stage is available for download.

The End-stage and the Battery Manager units are connected together with a high-voltage cable. The stimulating circuitry, and all its specifications are the same as described above at the Universal Floating End-stage. This version of End-stage is optimized for that aspect, that it does not generate any electric noise, because of this battery-powered scheme. According to this feature it can be placed close to the experimental object anywhere, even in a seriously shielded environment.

The complete User Manual of the Battery-supplied Floating End-stage, and the Battery Manager is available for download.

Constant Current LED Driver End-stage

It is used for Electro Retinography, and other light stimulating applications. It can provide calibrated current with 50 mA of full scale. Its internal construction is based on very high speed circuits for fast switching of the LEDs. Furthermore, there is an active current sink circuit to eliminate the parasite charge holding effect of LEDs.

Further development

Until now we have developed many different features for the BioStim system, as it is listed above. In spite of this, if you can not find the appropriate function for your special task in our actual choice, and this function seems to be interesting for other our customers, we will develop a special function especially for you. It is our method, how we improve the features of our equipment. We collect all the notices and feedbacks of our customers, and we implement their (may be your) knowledge into the features of BioStim.