Voltage Regulator Circuit Calculations

AI Thread Summary
To determine the output current after reducing voltage to 6V in a circuit with a 24V input, measuring the current is essential, especially since motor characteristics can vary. An ammeter can be used in series with the motors, but this may affect current readings due to the meter's resistance. It's also advisable to measure the current directly from the 24V supply to account for the regulator and resistors. The LM317 regulator has a current limit of around 1.5A, and the motor's current draw will depend on its load and characteristics, including locked rotor amps during direction changes. Proper heat sinking for the regulator is crucial to prevent overheating under high loads.
Alexander1
Messages
13
Reaction score
0
Hey Guys, so I'm just in need of some help in relation to finding the output current after the voltage has been dropped to 6V. The circuit has an input voltage of 24V and I've attached a photo of my circuit diagram. Hopefully I haven't made any errors in that, but I've tested the circuit and it does work effectively. The purpose of the circuit is to be able to flick between motors and also change their direction of rotation. The reason I need to know the output current is so I can find the power that each motor will require but I'm just a bit confused. Thanks.
upload_2017-5-7_14-30-46.png
 
Engineering news on Phys.org
You would have to measure the currents.

Unless the motor comes with information about how much current it draws when supplied with 6 volts and with different loads, the only way you can find out is to measure it.

You could put an ammeter in series with each motor, but this might cause the current to be reduced due to the resistance of the meter.

Or, you could put the meter directly after the 24 volt supply and measure the current there.

You could measure without the motors to work out how much is being used by the resistors and the regulator. Then subtract this from the figure you get with the motors running.
 
Last edited:
  • Like
Likes Alexander1
Thanks very much. The motors are micro metal gear motors so I'll have a look and see if they have that information.
 
Alexander1 said:
Hey Guys, so I'm just in need of some help in relation to finding the output current after the voltage has been dropped to 6V.

As VK6KRO has said, just measure it

Be aware that the LM317 like most other linear regulators have inbuilt current limiting --- check the specifics in the datasheet
it's somewhere around 1.5A
 
  • Like
Likes Alexander1
How much current is drawn depends on motor characteristics as VK6KRO and davenn have said, but also upon how much mechanical load is present at the motor shaft. The motors will have a full load current rating, and (possibly) a locked rotor rating.

Keep in mind that when flipping the direction switch the motor will pull LRA (Locked Rotor Amps) as it spins down before reversing itself. This can be quite a bit more than full load current, and may be enough to put the LM317 into overload limiting. If operating anywhere near the 1.5 amp rating bolt a fairly hefty heat sink to the regulator, or chances are good that it'll fry.
 
  • Like
Likes davenn and Alexander1
I used to be an HVAC technician. One time I had a service call in which there was no power to the thermostat. The thermostat did not have power because the fuse in the air handler was blown. The fuse in the air handler was blown because there was a low voltage short. The rubber coating on one of the thermostat wires was chewed off by a rodent. The exposed metal in the thermostat wire was touching the metal cabinet of the air handler. This was a low voltage short. This low voltage...
Hey guys. I have a question related to electricity and alternating current. Say an alien fictional society developed electricity, and settled on a standard like 73V AC current at 46 Hz. How would appliances be designed, and what impact would the lower frequency and voltage have on transformers, wiring, TVs, computers, LEDs, motors, and heating, assuming the laws of physics and technology are the same as on Earth?
Thread 'How Does Jaguar's 1980s V12 Dual Coil Ignition System Enhance Spark Strength?'
I have come across a dual coil ignition system as used by Jaguar on their V12 in the 1980's. It uses two ignition coils with their primary windings wired in parallel. The primary coil has its secondary winding wired to the distributor and then to the spark plugs as is standard practice. However, the auxiliary coil has it secondary winding output sealed off. The purpose of the system was to provide a stronger spark to the plugs, always a difficult task with the very short dwell time of a...
Back
Top