12VDC (0.35A) Motor with 1N4001 Diode?

I can't find any switching time specifications for this schottky diode so I don't know how to compare it to a 1N4001 but when I tried to research it I found this article which supports your recommendation of the 1n4001. In the absence of any data to support my claim I am forced to retract my statement that a schottky diode is better for a flyback application. If I knew how to compare the two in a side by side test I would do so.
If anyone wants to suggest a test I could obtain a schottky diode and give it go. I wouldn't know what frequency to use but I am fairly certain the standard switching test is a simple step pulse.
Another specification is the inductance of the test inductor. The arduino should be adequate to use as a pulse generator. The ball's in your court.

MarkT:
Typical slow diodes can have a sluggish turn on, ...

Not true.
They only have slower turn-off.

http://www.cliftonlaboratories.com/diode_turn-on_time.htm#Release_Time_Change

Turn-off times might be important for higher PWM frequencies though.
But I doubt it will make a difference for the default ~500hz of an Arduino.
Leo..

SCHOTTKY DIODE

When forward current flows through a solid-state diode, there is a small voltage drop across its terminals. A silicon diode has a typical voltage drop of 0.6–0.7 V, while a Schottky diode has a voltage drop of 0.15–0.45 V. This lower voltage drop can be used to give higher switching speeds and better system efficiency.
The Schottky diode is often used as a voltage limiter (aka clamp or bypass diode), in reverse bias. This is because the reverse bias voltage, the voltage at which it meaningful reverse leakage occurs, can be made quite low relative to other diode types, and in fact stable and specific. Schottky diodes for this use are sold by their reverse bias voltage spec. The impedance is quite low as with any diode in conducting mode. In effect it becomes a conductor at that voltage, and can be considered to be a switch.. "If reverse bias voltage >= X, then switch on ,otherwise remain OFF". This should not be relied on for high frequencies due to stability issues but the diodes are simply made stable for DC use ( perhaps to PWM frequencies ). The reverse bias voltage will not climb as any increase in current or voltage will simply bypass the protected circuit by easily passing through the diode, and yet if the applied voltage is not high enough, its not conducting.. The voltage is limited to be relatively close to the specified voltage.

FYI,
After rereading the schottky diode datasheet I found this:

*Pulse test: Pulse width 300 msec, Duty cycle 2%

Does it make good sense to use a Schottky diode if you are driving a inductance directly from an Arduino? Using a Schottky diode should ensure that the 'kick-back' current is taken by the diode, not by the protection diode within the chip.

Does it make good sense to use a Schottky diode if you are driving a inductance directly from an Arduino? Using a Schottky diode should ensure that the 'kick-back' current is taken by the diode, not by the protection diode within the chip.

That sounds like a good thing.
I did a diode switching test using this code:

void setup() 
{
  // put your setup code here, to run once:
pinMode(9,OUTPUT);
}

void loop() 
{
  // put your main code here, to run repeatedly:
digitalWrite(9,HIGH);
delayMicroseconds(6);
digitalWrite(9,LOW);
delayMicroseconds(294);
}

Test Pulse : 300 uS, 2% duty cycle
Vcc: 10V
Current : 0.150 A
Inductor : 100 uH rod inductor (choke)
Mosfet: FQP30N06
Filter cap from Drain to GND : 4 uF
diode UUT-1 : 1N4001
diode UUT-2 : STTH5128 (Fast Recovery diode) (body mass approx 4 times that of 1N4001
diode UUT-3 : 1.5KE350A (see datasheet link below) (body mass approx 10 times that of 1N4001

[1.5KE350A](ALLDATASHEET.COM - Datasheet search site, Datasheet search site for Electronic Components and Semiconductors and other semiconductors.

pdf/view/177493/VISHAY/1.5KE350A.html)

Observations: The 1N4001 had a perfectly flat response
Both of the other diodes had a rounded negative transition (rising edge was straight, first half of pulse was flat, then declined several volts during the second half of pulse .

1N4001 got hot too hot to touch and I could smell it overheating.
The other two diodes only got warm.
The 1.5KE350A ran the coolest of the three.
I can post scope shots if anyone is interested but didn't see any reason to.

NOTE: I know the other two diodes aren't rectifier diodes like the 1N4001 but I didn't have any other rectifier diodes on hand . I'll have to order some.

@raschemmel
Please show the 1N4001 vs 1.5KE350A

1.5KE are great for SWC on inputs with floating supplies to earth ground.

My comment that 1N4001 was not based on a detailed knowledge of this application, just a hunch that as a commonly used, general purpose device, it may be better to source a diode designed especially for this type of application. Low voltage drop, as mentioned is probably the main issue here, which should increase efficiency.

I am using a 1N4000 series diode across a 4 amp dc motor in a pwm app. It does get quite hot, and so I will be looking around for something more suitable.

@LarryD,
What is SWC ? (what does it stand for ?)

FYI,
This was a rush job because I only had 15 minutes before I had to leave for work so when I get home I can post some photos at a lower TIME/DIV so you can see the entire waveform. Also, I disconnected the smoothing cap (4uF) because it was masking the differences between the diodes.

The main difference is the 1N4001 is so hot you can't hold onto it for more than a second whereas the 1.5KE350A is cool enough to hold onto indefinitely.

SWC
Surge Withstand Capability

@raschemmel
For a fair test, could you compare a 1Amp normal diode with a 1Amp schottky diode.
e.g 1N4004 vs. 1N5819

In my previous posts I was fighting the fact that it's a common misunderstanding that "slow" rectifier diodes turn on slow.
That slow diodes turn off slow might not a problem for a relay/solenoid (switching once), but if you do that with a high-ish PWM frequency as in your test, I expect a common diode to get hotter.
Leo..

SWC
Surge Withstand Capability

That's what they use them for at work. Our product runs on 240vac so the peak voltage is SQR(2)=339.411, the 1.5KE350A is perfect for that voltage (350V-339V=10.588 V range between the peak operating voltage and the VBRNominal voltage for that diode.
datasheet

@Wawa,
I'll have to order the schottky unless I can find it at Fry's Electronics.

That's what they use them for at work.

:wink:

raschemmel:
@Wawa,
I'll have to order the schottky unless I can find it at Fry's Electronics.

The 1N5817, 1N5818, 1N5819 are common 1A schottky diodes.
Much like the 1N4001 - 1N4007
Leo..

I found this

(NTE is the Fry's brand of electronic components (made in China) . You need the NTE Cross Reference to find anything if all you have is an industry standard part number (like 1N5818) Once you have the NTE datasheet you can compare it with an industry standard datasheet
Look at the OnSemi datasheet , page -2, (Maximum Instantaneous Forward Voltage ) and then compare it to the specs on the NTE datasheet .

I order some 1n5817s from China (ebay). ($3.93 , free shipping)

@raschemmel
For a fair test, could you compare a 1Amp normal diode with a 1Amp schottky diode.
e.g 1N4004 vs. 1N5819

@Wawa,
I don't have either a 1N4004 or a 1N5819 (yet)

I was able to get a NTE 1n5711
1N5711
and a 1N5822

NTE 1N5822

VISHAY 1N5822

I don't know about you but I can't tell them apart.

TIME/DIV: 1uS
Amplitude: 5V/DIV
Vcc: 10V
Inductor: 100 uH choke
Mosfet: FQP30N06

Where are you measuring?

I expect the 1N4001 and 1N4004 to test the same.
The main difference is the reverse breakdown voltage, and you don't come even close to that.

The 1N5822 is a 3Amp schottky. You should compare that to a normal 3A 1N5400 series diode.

I think diode temperature is the thing you're looking for.
Most, if not all, diodes are fast enough to take the start of the back-EMF current.
Only the diodes that turn off faster are "ready" when the mosfet switches on again.
Leo..

Where are you measuring?

From GND to the drain of the mosfet.
Connections
Vcc => inductor-a
mosfet Drain => inductor-b
mosfet source => GND
mosfet gate => arduino pin
UUT DIODE-a => ACROSS THE INDUCTOR.

Did you want something different like from diode anode to cathode ?

I think diode temperature is the thing you're looking for.
Most, if not all, diodes are fast enough to take the start of the back-EMF current.
Only the diodes that turn off faster are "ready" when the mosfet switches on again.

I don't have apples to compare to apples or oranges to compare to oranges.
At the moment all I have is apples and oranges (1n4001, 1.5KE350A. 1n5711, & 1n5822)

I placed an order for 1N5818s but it's coming from China.
If I need something other than what I have now I will have to order it.

Across the inductor.