# L298N Voltage Drop Excessive (Solved!!)

Mine reads current but only up to 25 mA. Very little. Not useful for measuring the current in motors or so.

Grumpy_Mike: Well you won’t because that is a basic parameter of bipolar transistors, it is short for the Voltage between the Collector and Emitter when the transistor is in SATuration. That means is turned on as hard or as completely as it can go. So it is a bit like complaining they don’t say what a volt is.

I have not seen a multimeter that can’t measure current, even the \$5.00 from a thrift shop can measure current.

Well, I'm an Aeronautical Engineer and a Computer Analyst, but not by any means an Electrical Engineer. I took one class in College about 50 years ago, and about all I remember is that V=IR. So the terms you are using might just as well be Greek, the same way some of the spec sheets are relatively meaningless. So, guess what I am getting at is I enjoy tinkering, and Aduino is a hobby board to me and I suspect a lot of others. So it might be unrealistic to suppose everyone knows what these terms mean. We count on experts like Grumpy-Mike to shed light on these terms and in so doing educate us.

As for the multi-meter, I don't have enough experience to know one way or another whether every multi-meter will measure current, but I suspect there is a lower limit below which some cannot measure. I have two one a fluke I inherited and the other from HF, and neither could sense any current flowing from the power supply to the motor. That led me to the conclusion that either my multi-meters were both AOCP (thats an Air Force term meaning Aircraft Out of Commission for Parts)or the current was below the measurable threshold for my meters. So my question was looking for suggestions for a meter that would measure the typical current found in an Arduino circuit. Sorry if I didn't make that clear.

Hi, What are the model and part number of your DMMs?

Or a picture of them would help.

Thanks.. Tom.. :)

TomGeorge: Hi, What are the model and part number of your DMMs?

Or a picture of them would help.

Thanks.. Tom.. :)

Tom, Not in my shop right now, I'll post that information tomorrow morning when I get in.

Spec sheets are written for electrical engineers of course - and will use many more terms that you may not be familiar with, but all of which you can quite easily find online. For example,this tutorial about transistors. There are similar tutorials about all kinds of parts.

For your motors, you'll also have to look into H-bridges.

Of course it takes some studying to allow you to choose the correct parts for the project, but that's all just part of the hobby. It's not something you can get right without any knowledge on the parts you're using.

And for your amp meter... typical currents found in microcontroller circuits are from less than 1 uA to maybe 100 mA, while currents of peripherals go from less than 1 uA to many A. So that's a range spanning about 8 orders of magnitude.

wvmarle: And for your amp meter... typical currents found in microcontroller circuits are from less than 1 uA to maybe 100 mA, while currents of peripherals go from less than 1 uA to many A. So that's a range spanning about 8 orders of magnitude.

My new cheapie has current scales of 20uA, 200uA, 2mA, 20mA, 200mA and 10A.

wvmarle: Spec sheets are written for electrical engineers of course - and will use many more terms that you may not be familiar with, but all of which you can quite easily find online. For example,this tutorial about transistors. There are similar tutorials about all kinds of parts.

For your motors, you'll also have to look into H-bridges.

Of course it takes some studying to allow you to choose the correct parts for the project, but that's all just part of the hobby. It's not something you can get right without any knowledge on the parts you're using.

And for your amp meter... typical currents found in microcontroller circuits are from less than 1 uA to maybe 100 mA, while currents of peripherals go from less than 1 uA to many A. So that's a range spanning about 8 orders of magnitude.

But learning is half the fun of a new hobby. I have spent years learning how to make furniture, and an equal number of years learning how to restore old machines. So this is another of those hobbies that serve to keep the mind active and in so doing keep us young. For me most of the enjoyment is researching for answers. Its a little more difficult with this area since I have so little expertise and no background, but its like anything else, it all just takes time. And time I have plenty of right now.

I have been reading about H bridges. I spent most of today programming my project. I have the code pretty much in hand using the L298N I had on hand. Now I just need to determine the most efficient way to do what I want to do. Its actually pretty simple, program a controller so I can control the speed and direction of a 24V DC motor to use on my Rod turning lathe. I have the components pretty much figured, pot to control speed, I have developed code to handle that and have a pot on hand. Then button switches to control direction and two LEDs to show clockwise or counter clockwise. I have code running to do this too. And last a floor switch to turn the motor on and off. I haven't decided yet how to do that, either in series on the hot wire to the motor, or like a pushbutton to a data port on the Arduino. I could use a DC motor controller for this whole project, but Arduino seemed like a lot more fun.

Thanks for the information. Appreciate the insight and information.

wilfredmedlin: My new cheapie has current scales of 20uA, 200uA, 2mA, 20mA, 200mA and 10A.

Hmmm, neither of mine go that low. The HF one is .2 amps and the Fluke doesn't have any markings except the basic. I suspect the fluke has some capability I don't know how to use. Think I may have to google it to see what I am missing.

ov10fac: the Fluke doesn't have any markings except the basic. I suspect the fluke has some capability I don't know how to use.

Once you get the model number off it, I'm sure you'll be able to find the driver's manual online. Or if you post a pic or the model number, someone here may have used the same model and know its capabilities.

Just a point but you do know how to measure current with a meter. You have to break the circuit and insert the meter as if it were a piece of wire joining that break. You do not measure between two points like a voltage reading. If you do that on the current range you cause a short circuit and that is likely to burn out the fuse fitted to many meters so it will not measure current until this fuse is replaced.

Grumpy_Mike: Just a point but you do know how to measure current with a meter. You have to break the circuit and insert the meter as if it were a piece of wire joining that break. You do not measure between two points like a voltage reading. If you do that on the current range you cause a short circuit and that is likely to burn out the fuse fitted to many meters so it will not measure current until this fuse is replaced.

Oh yea. Learned that lesson the hard way many years ago. Accidentally had meter on Amps and tried to measure a 24 V voltage. Interesting results.

My Multi-Meter does measure Amps. I checked the manual on my Fluke 8205 and it measures down into the UA range, so I must have been doing something wrong. I will play with it when I get back later today.

Hi guys, sorry my English not good anymore. My issue is that when i supply control signal, the output is 10V and immediately drop to 0V. In the otherside, my l298n is too hot. I dont know what happen with my l298n, please help me!!!