What setup do I need to simulate a load and device?

Thread Starter

electabuzz

Joined Dec 5, 2014
5
Hi all!

I'm somewhat new to this kind of testing. I have a device that needs 24V but it's too expensive to test on. So I would like to be bale to simulate it somehow in hardware and put it inline with a toggle switch which I would also like to subject to ~24V/3A for an extended period of time.

Do I need a load generator and some kind of pseudo device to simulate this?

Any help would be great! Thanks!
 

ericgibbs

Joined Jan 29, 2010
15,726
hi electa,
One method I use for power supply testing are vehicle headlamp bulbs.
There are12V and 24V types available, choose the lamp wattages to suit your test.
E
 

Reloadron

Joined Jan 15, 2015
6,707
Hi all!

I'm somewhat new to this kind of testing. I have a device that needs 24V but it's too expensive to test on. So I would like to be bale to simulate it somehow in hardware and put it inline with a toggle switch which I would also like to subject to ~24V/3A for an extended period of time.

Do I need a load generator and some kind of pseudo device to simulate this?

Any help would be great! Thanks!
If I read you correctly you want to be able to place a 3 amp load on a 24 volt supply. Discounting any lead resistances you want an 8.0 Ohm load. Since you have 24 volts / 8.0 Ohms = 3.0 Amps. Your power dissipated will be 24 volts * 3 amps = 72 watts. I would just use a resistive load capable of dissipating 72 watts with overhead so maybe 100 to 125 watts. Two of these in parallel would likely work just fine. You can also as mentioned use for example 12 volt automotive lamps with pairs in series.

Doing any accurate test you may want to include a current and voltage measure. All you need in simple terms is a load and how exact you want to get is up to you.

Ron
 

Thread Starter

electabuzz

Joined Dec 5, 2014
5
If I read you correctly you want to be able to place a 3 amp load on a 24 volt supply. Discounting any lead resistances you want an 8.0 Ohm load. Since you have 24 volts / 8.0 Ohms = 3.0 Amps. Your power dissipated will be 24 volts * 3 amps = 72 watts. I would just use a resistive load capable of dissipating 72 watts with overhead so maybe 100 to 125 watts. Two of these in parallel would likely work just fine. You can also as mentioned use for example 12 volt automotive lamps with pairs in series.

Doing any accurate test you may want to include a current and voltage measure. All you need in simple terms is a load and how exact you want to get is up to you.

Ron

Interesting. And please correct my logic if I'm wrong:
-So you've got them in parallel to bring the total resistance in the circuit from 16ohms down to 8ohms (because they're each rated at 16ohm).
-Which will cause a 3amp load on the supply.
-Which means the circuit is burning ~72 watts.

I can see that on the Amazon listing that each of those resistors has 100W stamped on them. Is this just their max rating each? Because P=VI will still just draw 72W no matter what the item says since my load is limited by the resistance. Am I missing something?

How'd you get it up to 100-125W?

And, do you have any ideas on how I might measure the current and voltage accurately? Happy to purchase new devices if needed. The supply will likely tell me how much is being drawn but is that accurate enough or should I do more?

Thank you!
 
Last edited:

Reloadron

Joined Jan 15, 2015
6,707
Yes, you got it. The resistors will give you a 200 Watt load but the load will only dissipate what is there. So 24 Volts times 3 amps is 72 watts. I allowed overhead in the resistor wattage.

Now the trick is this. If I place the load on a battery the voltage will be dropping do the voltage will not be a constant. However if my load is on a Power Supply on mains power rated for the load things will be fine.

Years ago measuring voltage and current was much more of a challenge than today. There are plenty of inexpensive solutions. Keep in mind I am guessing SC volts and current from your supply source. Alec_t mentions that in post #3. I am assuming a constant mains powered DC supply. There are plenty of inexpensive off the shelf current measuring modules out there. Here is one example. Here is another example. Both modules require a 5.0 VDC supply. Here is an old fashion basic DC Analog Current meter. Current is measured in series with the load. Voltage is about the same with plenty of small digital DC Voltmeters out there inexpensive. Like current there are also basic DC old style analog voltmeters available.

You can pretty much have whatever you want from basic inexpensive to a data logger design which will record the data over time. All depends on exactly what you want to do and how you want to do it. Also how deep your pockets are. :)

Ron
 
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