Category Archives: Blog

Electronic Symbol and Components

Who Really Uses Electronic Symbol and Components?

Design Engineers, electrical and electronic technicians and craftsmen all use electronic symbol and components. They use them at one time or the other. The engineer use them as materials for his/her design work. Meanwhile, in time of electrical installation, fabrication, or troubleshooting, all the professionals make use of them.

Electronic circuit symbols are symbolic representation of electrical and electronic components in a circuit or schematic diagram. Combination of components in a circuit and how they relate to each other determines how the circuit function. Meanwhile, position of a component symbols be it parallel or series with others determines its function. However, if you know how, you can fashion out a wiring diagram from circuit and vice versa.

Printed Circuit Board (PCB) and wiring installation is a product of circuits/schematic diagram.

How to read and interpret a schematic diagram

To read a circuit, you begin to trace from the left side of the board. But you need to identify power source and switch from other components and how they interconnect. Reading and translating wiring diagram is a skill in troubleshooting. However, if you can read, understand and interpret a diagram, you can easily identify and isolate problem areas in equipment and appliances.

To acquire the skill is not difficult, all you need to do is to identify each component, know all about each component, understand how one component relates to the other. Meanwhile, understand basic parallel connection, series connection and series-parallel circuit theory.  Listed below are examples electrical electronic components symbols.

Example electronic components and symbols listed are Transformer, Headphone, diodes, transistor, resistor and lots more.

Click on any of the Symbols for expanded view.
electronic symbols typical

For an exercise, get a simple circuit online. Identify the components in the circuit. Then, explain how the circuit works. Finally you can post the circuit and your explanation in the comment, or send as a feedback

Medical Suction Machine Fails! What to do?

medical suction machine Medical suction machine is one of the must check before starting a case. An anesthesiologist think through and its of interest to run through a quick checklist of machine; monitors; suction ; airways; IV; drugs etc. to ensure all needed stuffs are intact. There is a necessity to check all equipment and accessories especially the monitor; the anesthetic machine; and the suction apparatus. Notwithstanding, the user checked the items for availability. A Biomedical Equipment Technician need to ascertain all equipment are in good order to function.

Equipment Checklist Before a Procedure

Check the monitors for appropriate probes and secure sensors in place. Sensors are prone to damage through rough handling so its important to keep spare to avoid disappointment, inconveniences and embarrassment. Suction machine on its part are prone to fail due to leakages. The leakages come through cracked and worn-out rubber gasket. This occur at the edge of the lid for the reservoir bottle or from leaks at the joints between the patient nozzle and the reservoir. Similarly, between the plastic tubing and the catheter.

When you have checked the bottle is well covered and well sealed, the gasket rubber may be worn. Similarly if you have a trusty patient plastic nozzle, yet the machine do not come up with usable suction pressure, then, you may need to check the pressure control knob if it’s opened. However, if this is o.k. then, you need to get inside the machine itself. However, someone with technical knowledge is suitable for this tasks because a novice may leave the machine worst than he/she found it.

Problems with Medical Suction Machine

However, do not dismay if you are just starting out but you have some basic technical knowledge, you can confidently open the machine to check little error such as disconnected tubing but if the problem is more than that supervision in the workshop by more experienced technician is necessary. Meanwhile, you can learn more about suction devices

The problem with the machine is probably caused by a leaky capacitor, or open fuse etc. or faulty electric motor especially if fluids managed to escape the cut-off-safety valve into the pump. After you the repair is complete and the machine is now sucking, for safety sake, carry out electrical safety test and do pressure calibration. You need to check the negative pressure with pressure meter and ensure it tally with reading on the gauge. To walk through necessary steps and to receive  updates information and support on medical suction machine and general medical equipment repair and management series, you can Subscribe to Our Mailing List and Newsletter or give your comment below.

Transistor Switch Design

Precautions Switching Inductive Loads

Many times we need to switch inductive load like solenoid valve through a transistor switch. In fact, some tasks require powering a heavy load via a relay or a contactor. The solenoid valve, relay or contactor and any device with coil primarily acts as an inductor. This is because it’s a coil and the inductors do not like sudden changes in current.

Watch this video for thorough understanding.

Source: Ben Krasnow

However, if you interrupts the current flowing through a coil suddenly, for instance when you open the switch. The coil will react with a sudden very large voltage across its leads. Thus causing a large surge of current through it due to collapsing magnetic field, within the coil as the current is interrupts abruptly. Surges in current resulting from inductive spike can results in thousands of voltage. The inductive spike will possibly harm neighboring devices within the circuit such as switches, transistors and relay contacts etc.

Transistor Switch Circuit

In the transistor switch circuit, a way out of inductive spike is to use what is known as transient suppressors. The suppressor interrupts the current through the coil. Typical transient suppressor is a diode across the relay coil in the relay driver shown below.

Fig 1Fig 1 Relay Driver

The circuit above is a typical transistor switch control driven by an input voltage. When sufficiently large voltage and input current applies to transistor’s base lead, the transistor’s collector-to-emitter channel opens. Thus allowing current to flow through the relay coil. Take note of the diode across the relay coil to eliminate imminent damage to the transistor by voltage spike through the switching of the coil.

Sometimes they use an RC network as a transient suppressor especially for relay using ac. But it’s important to use a resistor and capacitor with rating for a potentially large transient current suitable to the coil current.

In the AC Driven Coil with RC transient suppressor shown above, the capacitor absorbs excessive charge. Then the resistor helps control the discharge to safe limit. A typical RC network for small loads driven from the power line uses 100 Ω Resistor and 0.05 µF Capacitor.

Transistor switch snubber
RC Snubber Circuit from Wikipedia.