Voltage Regulation, Part 2 of 3

This part describes the circuits using the four regulators and the loads described in the first part

PT-PC021

Description

This switching regulator provides 500 mA of current to the circuit. This makes it ideal for small electronic circuits that don’t demand much. It has a peak current output of 1.5 A which means that it can provide 1.5 A of current, but only for a short period of time.

The regulator measures just under an inch (25.4mm) square and its main component is the MC34063 integrated circuit. It accepts an input voltage of 5 to 24 VDC. Although the output voltage is adjustable from 2.5 to 12 VDC the input voltage determines the maximum output voltage which must be 2 volts more than the output voltage. For example, if the input voltage is 10 VDC then the maximum output voltage would be 8 VDC.

Connection

Functionality

I built the four circuits mentioned.

I adjusted the regulator to feed 5 VDC to the LED circuit No surprise there. I then increased the regulator’s output voltage to 8 VDC. Again no surprise. The LED draws very litle current. The regulator hardly feels it at all.

Connected 12VDC lamp to regulator and provided 8 VDC. Lamp barely lit. I measured te Vout and found that with the lamp connected the output was around 1 VDC. I disconnected the lamp and the voltage went up to 8 VDC. It may be that this regulator could not handle the lamp’s current requirements.

To confirm this I used Ohm’s Law: V = IR. The voltage is 8 VDC and I measured the lamp’s resistance to be 6 Ohms. Since I am looking for the current I adjusted the equation:

I = V / R = 8 / 6 = 1.33 A

The regulator can provide 500 mA while the lamp draws 1.33A. Since the lamp draws more current than the regulator can provide, the regulator attempts to compensate by lowering the voltage. The lamp barely lighted, but it did light.

I connected a 12VDC fan to the regulator and supplied8VDC. All went well. I observed the circuit in action for a few minutes to see if the regulator would get hot. It did not. All components were cool to the touch. I then increased the voltage to 12VDC and observed for a few more minutes. The fan spun faster, the sound level went up but the regulator did not get any hotter.

I connected the voice recorder to the regulator and adjusted the output to 4.5 VDC, still keeping well below the advertised 5 V maximum. I tested the voice module a few time without incident and left it connected for a few minutes. The regulator did not get hot. The voice module draws little current and I suspect that it draws even less while idle.

PT-PC031
Description

This switching regulator provides 1.5 A of current to the circuit. This makes it ideal for electronic circuits that require 1 to 1.5 A. It has a maximum power output of 10 Watts. The PT-PC031 comes with a conversion or breakout board to facilitate wiring connections. In addition, this item also has various safety features to protect it from over-current, over-temperature and short circuits.

The regulator measures just an inch (25.4mm) square and its main component is the AX3022 integrated circuit. It accepts an input voltage of 4 to 24 VDC. Although the output voltage is adjustable from 2.5 to 18 VDC the input voltage determines the maximum output voltage which must be greater than the output voltage.

Connection

 

Functionality

I connected all four circuits to the regulator, varying the voltage according to the circuit’s safe operating voltage.

I fed 8 VDC to the LED circuit. It worked flawlessly. The regulator never got hot, as would be expected since the load had a small current demand.

I connected the small 12V DC lamp to the regulator and started out with 8 VDC. The lamp lit brightly. The regulator got hot within a short time and then it started shutting off intermittently. It was obvious that the regulator could not handle the lamp’s current demands. I lowered the voltage to 7.5 VDC; however, the intermittent shutdowns continued. Finally I tried 7 VDC and the lamp lit steadily without further shutdowns although the regulator still got hot.

This regulator provides 1.5 A and the lamp draws 1.33 A. While in theory this indicates that the regulator should provide enough current for the lamp, in truth it still got hot enough that the circuit closed down for its own protection. Using Ohm’s Law again with the 7 VDC shows the following:

I = V / R = 7 / 6 = 1.16 A

Now the current draw is low enough to allow the circuit to function without the regulator closing down every few minutes, albeit still a bit hot.

I connected the 12VDC fan to the regulator and started with 6 VDC. The fan whirred along without any problems. I raised the voltage steadily until it reached 10.2 V DC. Since my power supply provided 12.5 VDC the regulator was not able to provide more than the 10.2 V DC already mentioned. The regulator did not get hot. While the fan must have had a high current demand, it was not high enough to tax the regulator.

I connected the voice recorder module and provided 4.25 V DC using the regulator. This component’s maximum voltage is 5 V DC; therefore, I decided to keep within a safe acceptable range. The module also had a small current demand. The regulator never got hot and was able to handle the load without difficulty.

As an additional note, notice that the output has three pins. The top and bottom pins are for Vout and Ground. The one in the middle is used to enable or disable Vout. If the middle pin is connected to ground there will be no output voltage. For normal operation this pin should be left unconnected.

LM2596 2A

Description

This switching regulator provides 2A of current to the circuit. This makes it ideal for electronic circuits that require 1.5A to 2A of current. This regulator can provide up to 3A; however, a heat sink is required. In cases where more than 2 A are required it is best to locate a regulator that will provide the necessary current without straining it. I should note that the LM2596 datasheet lists the component as a 3 A device.

The regulator measures approximately 1.7 x .8 x .5 inches (43 x 21 x 14 mm) LxWxH and its main component is the LM2596 integrated circuit. It accepts an input voltage of 4.5 to 40 VDC. The output voltage is adjustable from 1.5 to 35 VDC. The input voltage determines the maximum output voltage which must be greater than the output voltage.

Connection


 

Functionality

As with the other circuits, I connected 5VDC and then 8VDC and observed the result. The circuit worked as expected.   

Using the 12VDC lamp I provided 8VDC and monitored the circuit for a few minutes. The regulator did not get hot.

I initially provided 8 VDC to the 12VDC fan. This circuit functioned well without any incident. I then began increment the voltage, making a stop at 10VDC. Still the regulator did not feel hot at all. I finally raised the voltage to 12VDC. I kept the circuit functioning for a few minutes to monitor the temperature; however, the regulator remained cool.

Next I connected the voice recorder to the regulator with an output of 4.5 VDC. I tested the voice module a few times and left it connected for a few minutes. The regulator did not get hot. The regulator had no problem with the voice module.

LM2577S + LM2596S dual chip 3A (max)

Description
This switching regulator provides up to 3A of current to the circuit. This regulator features both step up and step down functionality. Its core components are the LM2577S and LM2596S integrated circuits. This item is described as a “solar power supply module” which indicates that it is suited for solar power projects,

The regulator measures approximately 2.09 x 1.50 x 0.75 inches (5.3 x 3.8 x 1.9 cm) LxWxH. It accepts an input voltage of 3.5 to 28 VDC. The output voltage is adjustable from 1.25 to 26 VDC. The input voltage determines the maximum output voltage which must be greater than the output voltage.

Connection

Functionality

Once again I connected the simple LED circuit to 5VDC and then to 8VDC. This simple experiment had a casualty. Since I used a different breadboard which had an IC connected to it I did not notice that the IC’s voltage lines were connected. When I applied voltage for the first time sparks flew followed by a tiny mushroom cloud. The drama ended abruptly as the chip exploded. I rechecked everything and after verifying that the chip was the only casualty I continued with the experiments. Ironically, the chip was not part of the intended circuit nor was it intended to used at all for these experiments. Alas, poor LM339, I knew thee well.

I connected the circuit to the 12VDC lamp and applied 8VDC. The lamp lit correctly and after a few minutes of observation I did not notice any of the regulator’s components getting hot.

The fan circuit did not produce any surprises. The fan ran appropriately with both 6 and 12 VDC. The regulator did not heat up at either of these voltages.

I connected the voice module to the regulator and adjusted the output voltage to 4.5VDC. As with the other regulators, the voice module worked without any problems or heat.

The next and final instalment of this series will briefly discuss ripple, a characteristic that may make the output voltage slightly unstable and some thoughts on how to reduce it.

Where do you want to go? Part 1 Part 3

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