Our team at TechResource creates technical guides every now and then. These technical guides are explained from the perspective of a biologist and are a simple yet effective description about how things work. We also release trouble shooting guides, ready reckoner tables, etc. all of which are given to our clients in manuals, brochures etc. We have included here a list of
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List of Technical Documents
Sr. No. Topic Author Summary
1. Selecting a Power Supply (Part 1) Mustafa Motiwalla Selecting the right power supply is an important step for optimizing your molecular biology work in the lab. A well-designed, and well-constructed power pack can last a lifetime. The aim while deciding which equipment to buy should be - to procure the best that your laboratory would need, without spending too much for an equipment which is filled with features that you may never use. This article covers some of the important points and explanations of the many features such as CV/ CC, auto crossover, accuracy, chassis, and the operating temperature range.
2. Selecting a Power Supply (Part 2) Mustafa Motiwalla This article is a continuation of the earlier article. It covers some points such as features for safety, the requirement of wattage, insulation, tolerance to humidity
3. Selecting a Power Supply (Part 3) Mustafa Motiwalla This article is the culmination of the earlier two articles. It goes into details of wattage; what it means, and what is required. Concepts of wattage are explained as simply as possible.

High wattage vs Low wattage power supplies

Is a high wattage power supply better than a low wattage power supply? Or is it the reverse way around?

A common misconception is that a higher wattage power supply will consume more power and thus will be expensive to run due to the increased electricity consumption. This line of reasoning is faulty as it assumes that wattage is an indication of how much power is continuously consumed, whereas, it is only an indicator as to how much maximum power could be delivered.

To understand this better, lets talk about an analogous situation where you are looking to buy a car. The two options available to you are; a car with a top speed of 120 km/hr, and another with a top speed of 80 km/hr.

Some questions you may want to ponder over before making the decision;
- Would you want a car which can go to 120 km/hr, when required, or a car which can only go to 80 km/hr.
- Does having a car which goes to 120 km/hr mean it always has to run at 120 km/hr.
- If you were writing the specifications for a car you want to buy, would you not write "should go at least up to 120 km/hr" rather than to write "should not go beyond 80 km/hr".
Similarly, when you specify that the power supply "should not go above 80 W", you are limiting your output. Rather you should be writing "should deliver minimum 120 W".
This analogy can be better understood when the concept of wattage is clarified further.

What exactly is wattage and how is it calculated for a power supply?

The term wattage is used colloquially to mean electrical power in watts. Electric power is 'W' when a current 'I' consisting of a charge 'Q' coulombs every 't' seconds passes through an electric potential difference of 'V'
    Wattage = work done per unit time
                   = VQ/t
                   = VI                    (As I = Q/t)
i.e. Wattage = Voltage x Current
E.g. 120 W = 300 V x 0.400 A         (0.400 A is 400 mA)

When you run your gel at 100 V and the display shows that the current is 50 mA, the wattage can be calculated by
      100 V x 0.050 A = 5 W.
This means that; whether you have a power pack which goes to a max. of 120 W or 80 W; the wattage consumed at this moment is 5 W.

If you run your power pack at 300 V and the current is 267 mA, the wattage is
      300 V x 0.267 A = 80 W.
At this point, the maximum output of a 80 W power pack is reached. Hence, even if the specifications say that the power supply can go to 400 mA, in the current scenario, it will not go beyond 267 mA.

If you run your power pack at 300 V and the current is 400 mA, the wattage is
      300 V x 0.400 A = 120 W.
This power pack is now functioning at the maximum limit if it was a 120 W power pack.

Hence, a quick way to calculate the maximum wattage of a power supply should be to multiply the max. voltage possible with the max. current possible. But, many new power supplies do not seem to follow this principle. The wattage, does not seem to be a function of the max. voltage and current. This is because of the way the power supply has been configured. To keep the power pack light in weight; the wattage is kept low. But the drawback of doing this is that you can never achieve the maximum current and voltage at the same time.

Why are TechnoSource power supplies better than many competitor power supplies? (w.r.t. the maximum wattage)

All our power supplies are linear power supplies. i.e. their wattage can be calculated simply by multiplying the max. voltage and max. current.
Our power packs have higher wattages than most of our competitors, which as we have explained earlier, is a good thing. Hence you can run more gels, larger gels or more blots at the same time.

For e.g. On our power supplies rated at 300 V, 400 mA the wattage is 120 W. Here you can run two blots at 250 V, each consuming 200 mA; simultaneously.
      250 V x (0.200 + 0.200) A
      250 V x (0.400) A
      = 100 W

You can run four vertical apparatus at 300 V, each consuming 100 mA; simultaneously
      300 V x (0.100 + 0.100 + 0.100 + 0.100) A
      300 V x (0.400) A
      = 120 W

If you have any queries regarding power supplies and their use, please call us on 09819095429. We would love to help you.