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

Hi people.

I have 12VDC motor which draws 0.35A which is controlled by an Arduino.

Can I use 1N4001 diode to block voltage spikes?

Thanks in advance.

Yes. The diode goes across the motor. Cathode to +supply. What sort of transistor do you use to switch the motor. And what is the value of the base resistor. Leo..

You need to find out the maximum current draw (stall current), not just the nominal full-load current, since the transistor will have to survive these peaks too.

Can I use 1N4001 diode to block voltage spikes?

I think you mean flyback diodes to block inductive BACK EMF. (not voltage spikes)

raschemmel: I think you mean flyback diodes to block inductive BACK EMF. (not voltage spikes)

See "voltage spike" in the first sentence of this Wikipedia article.

However I believe "flyback diode" is derived from a diode used in some television line output circuits. Flyback is not a sudden voltage spike in my view.

I assume you are using PWM (and driving the motor via a transistor) and talking about the inductive kick when the motor is switch off. If you place a diode between motor +/- as suggested by wawa, this will prevent the voltage greatly exceeding the supply voltage. A 1N4001 should work OK but it is not the best for the job.

yendis:
A 1N4001 should work OK but it is not the best for the job.

Please explain.
Leo…

A 1N4001 should work OK but it is not the best for the job. Please explain.

Flyback diode is a SCHOTTKY DIODE application

A 1N4001 should work OK but it is not the best for the job.

From: motors, contactors , relays or solenoids I have never had any problems using a 1N4000 series diode in a fly-back application.

From: motors, contactors , relays or solenoids I have never had any problems using a 1N4000 series diode in a fly-back application.

Just for the record, neither have I.

raschemmel: Flyback diode is a SCHOTTKY DIODE application

Please explain.

Don't say: "becasue a schottky diode is faster". Because it isn't. At least not the "turn-on" time. Leo..

A schottky diode is not always the best, since the low on-voltage will slow down the current decay to perhaps twice as slow as a pn-junction diode, which might be too long for some applications.

For fast decay you can use a back-to-back zener+diode so that the voltage can be set for more rapid current decay. dI/dt = V/L

For a large electromagnet you might do the zener thing to make the thing let go quicker at turn-off

The speed of turn on isn't in the least bit critical so long as the device can prevent the forward voltage rising to the breakdown voltage of the switching device, not hard to achieve in practice.

Typical slow diodes can have a sluggish turn on, but you rarely see the transient Vf rising above a few volts even so, which is nothing for a free-wheel diode/snubber.

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](http://pdf1.alldatasheet.com/datasheet-

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

[u]Observations[/u]: 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.

1N4001_300_uS_2_percent_duty_cycle_10V_100uH.jpg|2285x1288

1P5KE350A_300_uS_2_percent_duty_cycle_10V_100uH.jpg|2285x1288

1N4001_VS_1P5KE350A.jpg|1143x644