Arduino Forum

Using Arduino => General Electronics => Topic started by: beingobserver on Dec 14, 2015, 07:55 pm

Title: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: beingobserver on Dec 14, 2015, 07:55 pm
Hi people.

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

Can I use 1N4001 diode (http://www.diodes.com/_files/datasheets/ds28002.pdf) to block voltage spikes?


Thanks in advance.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 14, 2015, 08:56 pm
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..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: MarkT on Dec 15, 2015, 12:34 pm
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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 16, 2015, 04:10 am
Quote
Can I use 1N4001 diode to block voltage spikes?
I think you mean flyback diodes to block inductive BACK EMF. (not voltage spikes)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Archibald on Dec 16, 2015, 11:48 am
I think you mean flyback diodes to block inductive BACK EMF. (not voltage spikes)
See "voltage spike" in the first sentence of this (https://en.wikipedia.org/wiki/Flyback_diode) 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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: yendis on Dec 16, 2015, 02:22 pm
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. 
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 16, 2015, 08:04 pm
A 1N4001 should work OK but it is not the best for the job. 
Please explain.
Leo..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 16, 2015, 09:35 pm
Quote
A 1N4001 should work OK but it is not the best for the job. 
Please explain.
Flyback diode is a SCHOTTKY DIODE (https://www.sparkfun.com/products/10926) application
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 16, 2015, 09:45 pm
Quote
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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 16, 2015, 11:13 pm
Quote
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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 16, 2015, 11:36 pm
Flyback diode is a SCHOTTKY DIODE (https://www.sparkfun.com/products/10926) application
Please explain.

Don't say: "becasue a schottky diode is faster".
Because it isn't.
At least not the "turn-on" time.
Leo..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: MarkT on Dec 17, 2015, 02:21 am
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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 17, 2015, 03:11 am
I can't find any switching time specifications for this schottky diode (http://cdn.sparkfun.com/datasheets/Components/General/1N5819.pdf) so I don't know how to compare it to a 1N4001 (http://www.vishay.com/docs/88503/1n4001.pdf) but when I tried to research it I found this (http://electronics.stackexchange.com/questions/110574/how-to-choose-a-flyback-diode-for-a-relay) 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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 17, 2015, 03:41 am
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..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 17, 2015, 04:14 am
SCHOTTKY DIODE (https://en.wikipedia.org/wiki/Schottky_diode)

Quote
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:
Quote
*Pulse test: Pulse width 300 msec, Duty cycle 2%
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Archibald on Dec 17, 2015, 06:38 am
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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 17, 2015, 07:56 am
Quote
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:
Code: [Select]
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 (https://www.radioshack.com/products/radioshack-100-h-rf-choke?variant=5717358789))
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)

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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 17, 2015, 08:25 am
@raschemmel
Please show the 1N4001 vs 1.5KE350A

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

Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: yendis on Dec 17, 2015, 11:20 am
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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 17, 2015, 02:50 pm
@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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 17, 2015, 06:58 pm
SWC
Surge Withstand Capability
(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=147426)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 17, 2015, 08:14 pm
@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..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 17, 2015, 08:55 pm
Quote
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 (http://www.st.com/web/en/resource/technical/document/datasheet/CD00000663.pdf)

@Wawa,
I'll have to order the schottky unless I can find it at Fry's Electronics.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 17, 2015, 09:13 pm
Quote
That's what they use them for at work.
;)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 17, 2015, 09:43 pm
@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..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 18, 2015, 05:50 am
I found this (http://www.nteinc.com/specs/500to599/pdf/nte585.pdf)

(NTE is the Fry's brand of electronic components (made in China) . You need the NTE Cross Reference (http://www.nteinc.com/quickcross/) 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 (http://www.onsemi.com/pub_link/Collateral/1N5817-D.PDF)
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)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 03:58 am
Quote
@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 (http://www.nteinc.com/specs/500to599/pdf/nte583.pdf)
1N5711 (http://www.st.com/web/en/resource/technical/document/datasheet/CD00000759.pdf)
and a 1N5822


NTE 1N5822 (http://www.nteinc.com/specs/500to599/pdf/nte586.pdf)

VISHAY 1N5822 (http://www.jameco.com/Jameco/Products/ProdDS/177990.pdf)

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
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 19, 2015, 04:49 am
Where are you measuring?
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 19, 2015, 05:01 am
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.

https://en.wikipedia.org/wiki/1N4001_and_1N5400_series_diodes

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..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 05:04 am
Quote
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 ?
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 05:08 am
Quote
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.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 19, 2015, 05:47 am
Across the inductor.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 06:01 am
Quote
Across the inductor.
That's a show stopper.

 Even with both my power supply and my scope both plugged into 3-prong to 2-prong
adaptors (http://www.cablewholesale.com/products/power-products/power-cords/product-30w1-32200.php?utm_source=GoogleShopping&utm_medium=cpc&utm_term=30W1-32200&utm_campaign=3%20Prong%20to%202%20Prong%20Grounding%20Converter%20for%20AC%20Outlet&gclid=CjwKEAiA-s6zBRDWudDL2Iic4QQSJAA4Od3XT3oz9qpzkFKLB2wAOgZB0oKr7KQUyL_klLrwRkMehRoCnqPw_wcB) my power supply shuts down (goes into current limit shutdown mode) if the scope ground touches either Vcc (cathode)  or the drain (anode) of the diode and I don't have a DIFF PROBE.

I have no way to measure across the inductor without a diff probe.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 19, 2015, 06:24 am
Even with the scope isolated from earth ground?
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 06:29 am
Quote
Even with the scope isolated from earth ground?
YES.

The only chance I have of obtaining that measurement is if I make my own DIFF probe, because I sure as hell can't afford to buy (http://www.ebay.com/itm/TEKTRONIX-P5200-HIGH-VOLTAGE-DIFFERENTIAL-PROBE-25MHz-/231783940275) one.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 19, 2015, 07:05 am
Makes no sense to me why there is a connection to earth if the ground lead is gone.
Never seen that.

The scope isn't pushed against another grounded piece of test gear?

When you measure with a DVM what resistance do you see scope chassis GND to the AC plug pins.
(Things powered off obviously).
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 07:13 am
Open
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 19, 2015, 07:31 am

 :o

Same with the other equipment I assume (ass u me ;) ).

Well, one option is to keep an eye out for a 1:1 isolation transformer to power the scope.

Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Wawa on Dec 19, 2015, 08:13 am
AFAIK it's common for the scope to be grounded, and the supply to "float" (except for the metal case).
So you can combine supplies for double voltage, double current, or a bipolar supply (one with positive to ground).
Some lab supplies have a third ground terminal.
Leo..
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 19, 2015, 08:26 am
Quote
AFAIK it's common for the scope to be grounded,
Yes.
For protection.
Never defeat the earth lead or use an isolation transformer unless you are 100% sure you understand the ramifications of doing so.

You can use a scopes math function and two channels to do differential measurements.

Of course you can power your circuit with a battery (or isolated supply) not having any part of the device referenced to earth.
You can then reference anywhere.
.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: TomGeorge on Dec 19, 2015, 08:38 am
Hi,
I assume your CRO is  single channel?

Tom.... :)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 05:07 pm
Quote
I assume your CRO is  single channel?
  
Look again

(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=147616)

FYI,
I have some LT1215s and I  have already used them for Differential Amplifiers in other posts so that's no problem but I don't yet know how to combine them opto isolators to make an isolated DIFF AMP,
not that it is necessary.

Note: Look at the red price tag... :D
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: yendis on Dec 19, 2015, 09:13 pm
If your scope has 'invert' on one channel, and 'add channels' mode your display will read differentially.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: TomGeorge on Dec 19, 2015, 11:00 pm
Hi,

Quote
If your scope has 'invert' on one channel, and 'add channels' mode your display will read differentially.
Exactly..

Tom.... :)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 19, 2015, 11:21 pm
which channel goes where and which one gets inverted ?
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: TomGeorge on Dec 19, 2015, 11:32 pm
Hi,
Select,   VERT MODE --   ADD
Select   CH2 POL  --  INV (I think button in)

Place both channels on same V/div

Use CH1 and CH2 as differential inputs.


Result on screen,   CH1 - CH2 = differential voltage.

Tom.... :)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 20, 2015, 01:05 am
I'm measuring across a diode. Which channel goes on the positive side of diode (cathode) and which goes on the negative side of diode (anode) ?
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: Archibald on Dec 20, 2015, 02:20 am
Raschemmel,

Perhaps I'm totally confused and have not read this thread carefully enough, but I suspect the measurements you have been making of the coil with diode are not valid at all.  I was alerted to this and puzzled a while ago by the oscilloscope traces you posted that showed the voltage going up to about 17V despite the presence of the diode, even allowing for some forward turn-on time.

What I think is happening with your test circuit is as follows.  The coil (choke) you are using looks here (https://www.radioshack.com/products/radioshack-100-h-rf-choke?variant=5717358789) as if it will have a resistance of only a few mΩ.  So, even with the pulse duration of only 6μs, I believe you are virtually shorting out your 10V power supply. My hypothesis is that the voltage going up to 17V and then ringing is simply the response of your power supply recovering after the short-circuit.  Does this make sense?

I suggest you use a relay coil instead of the 100 µH radio frequency choke.

I also suggest you temporarily replace the coil and diode by a resistor having a resistance fairly close to the resistance of your coil. You will then be able to check whether you get nice fast transitions displayed on your oscilloscope.  Have you trimmed (compensated) your oscilloscope probes?

I don't understand all the fuss in this thread about measuring across the inductor.  I suggest you continue to measure at the MOSFET drain but also check (using the other channel of your oscilloscope) that your 10V power supply remains essentially constant throughout.  You may need to add decoupling to the 10V power supply (close to the coil and MOSFET).  If your 10V supply is constant, there is no need to make differential measurement across the inductor.
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 20, 2015, 02:26 am
There is no fuss about measuring across the inductor, it was just curiosity.

Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 20, 2015, 02:29 am
  
Quote
I believe you are virtually shorting out your 10V power supply
Here you are mistaken. The power supply current was posted in the first photos and the power supply voltage is rock solid at 10 V. There is no shorting out of anything (unless I connect my scope probe ground clip to any point in my circuit). It's a bench LAB supply with adjustable current limit and both voltage and current displays. The photos posted clearly show the pulse (not a short).
The whole point of this measurement is to compare diode response, hence the measurement across the diode. Previously I didn't know how to do that because I can't connect my scope ground to any point on the circuit.


@LarryD,
It worked.

ch-1 on cathode
ch-2 INVERT on anode
VERT MODE SELECT: ADD
Vcc: 10V
TIME/Div: 10 uS
Amplitude: 2V/Div
Test Pulse: 300uS , 2% duty cycle

1N4001
(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=149691)

1N5711
(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=149693)

1N5817


(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=149695)
1N5822

(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=149697)


STTH 3R02

STTH 3R02 DATASHEET (http://www.farnell.com/datasheets/1817538.pdf)
(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=149699)

NO DIODE
(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=149701)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: larryd on Dec 20, 2015, 04:21 am
@raschemmel
Nice.
It appears the transorb and 1N4001 can handle the kick back differently (better?), interesting.
I have never used Schottky diodes for snubbing.

The transorb is designed to recover from high energy transients, they are more expensive.
It does appear they may have application where heating may result.
Over the years, I have also used MOVs in SWC designs.

At $95 you better get a second scope for spares.  ;)
Title: Re: 12VDC (0.35A) Motor with 1N4001 Diode?
Post by: raschemmel on Dec 20, 2015, 04:40 am
The Schottky diode scope shot is proof that there is a back EMF.


I bought the scope at a surplus store and it still has the name of the company that  owned it (IEM SENSORS) stencied on top. They must have had it calibrated because everything works.



(http://forum.arduino.cc/index.php?action=dlattach;topic=365774.0;attach=147756)

From the photo of the inductor response with no diode it looks like the back EMF negative voltage is at least 6V