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Home » Motor Circuits » Surge Suppressors »
Water Sensors »
Adding a Soft Start to Water Pump Motors - Reducing Relay Burning
Problems

By Swagatam Majumdar
9/27/2012 Motor Circuits Surge Suppressors Water Sensors

Adding a Soft Start
to Water Pump Motors - Reducing Relay Burning Problems

When heavy motor systems or
high current motors are involved, initial switch ON current surge often becomes
an issue. This surge tends to inflict huge sparking across the pump relay
contacts causing corrosion and reduction in its life due to stress,
and wear and tear.

The sparking of the motor not only
causes relay contact issues, but also affects surrounding electronic
circuits, causing them to hang or get disturbed due to large amount of
RF interference generated during motor switch ON.

However
safeguarding the costly motor relay becomes the main issue with such situations.
Though there are many mechanical contactors available for controlling motor
stress, these system are not efficient and are ineffective against the
RF emissions.

The simple electronic circuit presented below hopefully is
able to eliminate all issues concerned with heavy motor switch ON surge
generation and relay contact protection.

The figure shows a simple dimmer
switch circuit incorporating an ordinary triac and diac configuration, which can
be very effectively used for adding a soft start to any high current, heavy AC
motor.

Here the control pot has been replaced with a LED/LDR box. As we
know that in normal dimmer switches, a variable resistance is used for
controlling the fan speeds. Here the variable resistance is replaced with a
LED/LDR arrangement. It means now the speed of the motor, or in other
words, current to the motor can be controlled by controlling the
intensity of the enclosed LED through an external trigger.

That's exactly
what is done here. When the motor relay is switched ON, either by a switch or
through an electronic control circuit such as a water level controller circuit,
the LED of the attached dimmer switch is also switched ON
simultaneously.

The LED switches ON the triac and the connected
motor.

Being a solid state device the dimmer switch acts a little faster
than the relay and therefore the motor is first activated through the dimmer
triac and just after a few milliseconds the triac gets bypassed by
the concerned relay contacts.

The above process completely
eliminates any sparking from the relay contact since the triac has already
absorbed much of the current and the relay only has to softly takeover the
already switched ON motor conduction.

Here the brightness of the
opto-coupler LED is crucial, and must be set such that the triac is
only 75% ON.

This adjustment will save the triac from initial heavy
current transient and help the entire system to last for many many
years.

The resistor R4 may be appropriately set for achieving an optimal
glow over the LED.

Parts List

R1 = 15K
R2 = 330K,
R3 =
10K,
Diac resistor = 100 Ohms,
R4 = to be adjusted as explained,
C1 =
0.1uF/400V
C2, C3 = 0.1uF/250V,
L1 = 10 amp/220V choke
Triac
(Alternistor) = 10 Amp 400V,
Diac = as per the above
triac.

Simplified Version

A little inspection reveals that the
circuit actually does not require the opto coupler circuit at all. The
circuit may be simply arranged in the following manner:

R2 should
be selected such that the triac conducts only 75% of the power.

When
power is switched ON,  the triac provides a
soft initial start to the motor until within the next split second
when the relay also conducts enabling the motor the required full power. This
completely safeguards the actuator contacts from the initial current
surges and sparks,

Much Improved Circuit

As rightly
suggested by Mr.Jim, an initial torque is imperative
for initiating a motor optimally especially when it's loaded, if this
initial torque is absent. the motor might stall with heavy loads under its belt
and might start smoking within minutes.

The following circuit is
designed for solving both the issues together, it inhibits the initial surge
current to the ON/OFF switch and yet allows the motor to start with a "kick" so
that it initiates without problems even when it's loaded.

An ultimate PWM based motor soft start circuit can also be tried for
getting a better control, a better torque and a reliable startup for the
connected motor, even for 3 phase motors.

Tweet

92 Responses to "Adding a Soft Start to Water Pump Motors - Reducing Relay
Burning Problems"

Vineesh kodambattilOctober 7, 2012 at 7:08 PM

hi,
thanks for the post.in this
ckt, will choke create back emf and make any restriction of current to
motor?can we eliminate the electromagnetic relay by using triac of high ampere
say 30 amp?Solid state relay of 10 amp/400v available in market cost around
700 Rs.if can substitute this circuit will be a great thing.
thanks&
regards
vineesh kodambattil
ReplyDelete

Replies

SwagatamOctober 7, 2012 at 8:36 PM

Hi,

Thanks! The choke is
quite small so won't affect the motor.
Yes definitely an SSR can be used
in place of a relay, and in fact that would possibly eliminate all issues
normally encountered with relays.... however they are much costlier than
relays.

Regards.
Delete

Reply

info rainsOctober 11, 2012 at 2:27 AM

Hi Bro..

How can I connect
this above circuit with This one? (Semi Automatic Water Level Controller/Timer
Circuit).
http://3.bp.blogspot.com/-og5qPzr6Ioc/T5F_zVXMgqI/AAAAAAAABIA/KSrQtaGVZzQ/s1600/semi+automatic+water+level+timer+circuit.png
ReplyDelete

Replies

SwagatamOctober 11, 2012 at 9:55 AM

Hi Bro,

The RL1 contact
connections in your link should be replaced with the "motor relay" in the
above diagram.

The "from circuit" points in the above diagram should
be connected across C3 of the diagram in your link.

But first you
will have to make the triac circuit section as shown in the above
article.
Delete

Reply

AnonymousOctober 24, 2012 at 2:44 PM

LOL invented
ReplyDelete

SwagatamOctober 24, 2012 at 4:22 PM

Noun:invention,
in'ven-shun

The creation of something in the mind.

The creation
resulting from study and
experimentation.

Verb-invent
Adjective-inventive.

courtesy -
Wordweb
ReplyDelete

Simon OrdazDecember 5, 2012 at 6:49 PM

hello ..
very interesting your
circuit that would be the choke value here is hard to find but I have the
opportunity to do so, thanks and good luck.
ReplyDelete

Replies

SwagatamDecember 6, 2012 at 11:51 AM

Thank you very much!
Delete

Reply

amir gujjarJanuary 28, 2013 at 3:13 PM

hello dear,
plz tell me about the
" From circuit ". i hv no idea about that...??? reply me soon
ReplyDelete

Replies

Swagatam MajumdarJanuary 28, 2013 at 8:14 PM

it's from the trigger circuit or
the ON/OFF switch....
Delete

Reply

Amin JabariFebruary 1, 2013 at 6:03 PM

hi
i'm planning to build a soft
starter for single phase whitch is used in a vaccum cleaner.as you know vaccum
cleaner would be started manually by a person. so i think there is no relay in
its circuit. is it possible to put this circuit to this motor to reach a
softly starting goal?
thanks

ReplyDelete

Replies

Swagatam MajumdarFebruary 1, 2013 at 9:35 PM

Yes, according to me the circuit
would work for your application.

Delete

Reply

Amin JabariFebruary 2, 2013 at 1:58 AM

so can we subtitute the MOTOR RELAY
with a solid ON/OFF switch?
using a relay in a circuit encreases the cost
and couses lots of other problems.so it would be better not to use this
element
you have replaced the motor relay with a actuator contact in
simplified version.is that mean a simple on/off switch?
thanks and
regards
ReplyDelete

Replies

Swagatam MajumdarFebruary 2, 2013 at 3:52 PM

Yes you may replace the actuator
contacts with a solid 30 amp ON/OFF switch, or even by a relay, but with a
relay you will need a DC supply for the coil, input derived from the above
circuit mains points.
Delete

Amin JabariFebruary 2, 2013 at 6:12 PM

why 30 amp? if we use this for a
motor with 1kw-2kw power the nominal current is lower than 30 amps.you
haven't mentioned any special motor power for this circuit.so is it suitable
for any power range?(after adjusting R2 to reach 75% of nominal current)or
need some changes?
thanks and regards
Delete

Swagatam MajumdarFebruary 2, 2013 at 8:44 PM

It is safer to use bigger relays,
however since a soft start arrangement is included, lower rated relays would
also work.

The triac rating will decide what motor would safely
operate with the circuit.

Delete

Reply

Giuseppe GoriFebruary 3, 2013 at 12:19 PM

I am not sure I understand the
"simplified version".
You say: "When power is switched ON,...", but no
switch is indicated.
I assume you will use a 2-pole switch to control the
actuator and at the same time power on your circuit?

ReplyDelete

Replies

Swagatam MajumdarFebruary 3, 2013 at 2:56 PM

It should be a relay and not an
actuator....I will correct it soon.
Delete

Reply

Amin JabariFebruary 4, 2013 at 5:38 AM

with this modified circuit we can't
use solid ON/OFF switch instite of relay,can we? and what is the best option
for these upcoming parameters?
1.relay coil voltage
2.starter switch
current
3.relay current

when there is no circuit which is attached
to a motor,it starts just with a solid switch with high reliability(you have
added lately)
when we plug the circuit which is using a relay to the motor,
the reliability of the entire system decreases. is there any way to increase
this reliability and keep the price reasonable?(using SSR is a good option but
it increases the cost)
ReplyDelete

Replies

Swagatam MajumdarFebruary 4, 2013 at 7:14 PM

A relay is required here, without
it the circuit would become meaningless.... a small spdt switch can be used
for initiating the whole action.
Delete

Reply

Giuseppe GoriFebruary 4, 2013 at 8:58 AM

Thanks. Now I think I
understand.
The relay will close probably some 50ms after the circuit is
powered and this protects the contacts. It may also "soft start" a small
motor.

It may be useful to "ramp" up the current (especially for big
motors - I would like to use it on a 5HP pump). Can the Triac be driven with
some delay to go: 25% for 1s then 50% for 1s then 75% for 1s then close the
relay? Does this make sense to you?
ReplyDelete

Replies

Swagatam MajumdarFebruary 4, 2013 at 2:05 PM

Yes, definitely that makes
sense....the first circuit would be more suitable for this
application.

We just have to connect the LED with a slow rise type of
delay circuit which would initiate the triac gradually from zero to max
within a couple of seconds.

In fact in that case we wouldn't need the
relay at all.

Nowadays we have traics which are able to handle in
excess of 25 amps, they are better called alternistors.
Delete

Reply

Giuseppe GoriFebruary 5, 2013 at 5:09 AM

OK, so: No relay, New Triac >25A
(I assume new values for the other components as well?). Now, do you have
somewhere else a diagram for a "slow rise" type of delay?

ReplyDelete

Replies

Swagatam MajumdarFebruary 5, 2013 at 12:19 PM

if we connect a 220uF/25V
capacitor across the LED in the first diagram might produce the intended
results...R4 will need to be adjusted so that it operates directly from the
mains input....a 5K/10 watt may be tried initially.
Delete

Reply

Amin JabariFebruary 5, 2013 at 7:18 PM

could you please apply these
changes?

ReplyDelete

Replies

Swagatam MajumdarFebruary 6, 2013 at 11:26 AM

applied....
Delete

Reply

AnonymousFebruary 6, 2013 at 5:13 AM

Swagatam,

great help on
circuits thanks !

remember when slow starting motors especially larger
ones we need to give a warning that if they are under load at start like water
pumps (with back head pressure) air compressors, and some other belt driven
machinery.

They can over heat the motor if it can not overcome the
initial starting torque required by the load and it ends up just stalling as
the soft start kicks in.

this circuit works well for fans, blowers,
pumps under no head pressure, certain wood working
cutters.

Jim

ReplyDelete

Replies

Swagatam MajumdarFebruary 6, 2013 at 10:40 AM

Thanks Jim!

You are
correct, but in the above circuits the motor would be allowed the full power
within a couple of seconds, so probably there's no danger of motor getting
hot even with a load connected.

The concept is intended for
safeguarding the switching contacts from wear tear and from getting burnt
due to initial high current surges.
Delete

Swagatam MajumdarFebruary 6, 2013 at 10:49 AM

Jim, I have modified the circuit
in the above article, I think it hopefully solves all issues now.
Delete

Reply

Tayyab KamalFebruary 7, 2013 at 12:51 AM

hi i want a soft starter just for 1
hp motor which circuit of soft satrter should i use? can u plz tell
me?
ReplyDelete

Replies

Swagatam MajumdarFebruary 7, 2013 at 10:37 AM

use the last circuit.
Delete

Tayyab KamalFebruary 7, 2013 at 11:26 AM

thanks dear

Delete

Reply

AnonymousFebruary 7, 2013 at 3:44 AM

"motor would be allowed the full
power within a couple of seconds"

according to your comments, soft
starting option of this circuit changes to just protecting switchs,is that
right?

ReplyDelete

Replies

Swagatam MajumdarFebruary 7, 2013 at 9:26 AM

yes it's basically intended for
protecting the switch burning problems, but the last circuit hopefully takes
care of all the other issues also...
Delete

Reply

AnonymousFebruary 8, 2013 at 2:15 PM

do you have any idea to include the
soft starting option in this circuit for extending the lifespan of the
system?
ReplyDelete

Replies

Swagatam MajumdarFebruary 8, 2013 at 8:45 PM

a soft start is already included
in the last circuit (with the 100uF/25V cap) however the transition would be
relatively quick.
Delete

Reply

AnonymousFebruary 10, 2013 at 10:01 AM

How can i connect the last circuit
with my motor control
circuit?
http://homemadecircuitsandschematics.blogspot.com/2012/02/how-to-make-ideal-automatic-water-level.html
ReplyDelete

Replies

Swagatam MajumdarFebruary 10, 2013 at 9:35 PM

what is your motor control
circuit?
Delete

AnonymousFebruary 11, 2013 at 9:10 PM

I gave the link in my comment
above.

homemadecircuitsandschematics.blogspot.com/2012/02/how-to-make-ideal-automatic-water-level.html
Delete

Swagatam MajumdarFebruary 11, 2013 at 10:18 PM

explain your requirement in
details...
Delete

Reply

Anioko JamesFebruary 11, 2013 at 11:58 AM

thanks so much Sir for your good
work and am always praying to God to keep blessing you for your good work. i
designed the circuit using GSM to control house appliances but it not
responding yet, C1 and C5 capacitor has polarity but am confused of how to
connect their negative terminals. thanks so much Sir.
ReplyDelete

Replies

Swagatam MajumdarFebruary 11, 2013 at 9:41 PM

Thanks Anioko,

Please post
your question in the relevant article because I am confused which circuit
you are referring to.
Delete

NickOctober 16, 2013 at 12:26 PM

Hi

I am having trouble
getting this to work. I think that all of my wiring and components are good
and the right way round, except that the impedance for the relay is 1550
ohms. What might I change to get it to work? Or any other
suggestions

Thanks
Delete

Swagatam MajumdarOctober 16, 2013 at 2:10 PM

The last circuit had issues with
the diode and the switch positions, I have corrected them, it should work
now.

Delete

Reply

AnonymousOctober 16, 2013 at 7:10 PM

Hi Swagatam
In relation to the
much improved circuit from Mr Jim, I can't get the circuit to work. The relay
I'm using is 360 ohms (It's a Finder 41.61.9.012) but other than that
everything else seems in order. The draw from the motor will blow a 13 amp
fuse if started when not warmed up. I have another relay that is DPDT and has
a 200 ohm 12V coil but I don't know if that would work? Any
suggestions
Thanks Nick Gardiner
ReplyDelete

Replies

Swagatam MajumdarOctober 17, 2013 at 9:41 AM

Hi Nick,

I have answered
your issue in the previous comment, the circuit needed some corrections and
it's been updated in the new diagram, please check it out....your relay is
OK.
Delete

AnonymousOctober 22, 2013 at 2:51 AM

That's brilliant Swagatam. Thank
you.
Nick
Delete

Reply

AnonymousOctober 25, 2013 at 1:27 PM

Hi again

The new circuit
seems to work in that the relay is constantly switching but the motor is not
running. Could this be due to the circuitry in the cut out switch on the motor
side of this circuit?

Nick
ReplyDelete

Replies

Swagatam MajumdarOctober 25, 2013 at 6:01 PM

The circuit is actually pretty
simple: If the relay contacts close, the triac would get the gate current
and activate any load that's connected with its shown leads. So there's no
chance the motor won't run.

You can replace the motor with a light
bulb and check the response, if still it doesn't work then surely the triac
pinouts may be wrongly configured or due to some other connection
fault.
Delete

Reply

AnonymousOctober 25, 2013 at 8:42 PM

Hi Swagatam,

Thanks for the
quick reply. The relay is switching on and off repetitively, rather than going
from one state to the other, both on the big motor and on a small load. The
triac is connected right according to the datasheet.

Any other
suggestions?

Nick
ReplyDelete

Replies

Swagatam MajumdarOctober 26, 2013 at 3:32 PM

Hi Nick,
Replace the capacitor
across the relay coil with a 100uF/50V, this will surely rectify the
issue.
Delete

Reply

Udit SolankiNovember 4, 2013 at 8:21 PM

Hi Bro..

How can I connect
this above circuit with This one?
http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-build-gsm-based-cell-phone.html

i
want to start a 3 phase induction motor using this circuit..
ReplyDelete

Replies

Swagatam MajumdarNovember 5, 2013 at 12:44 PM

I am sorry Udit, all my circuits
are for single phase applications, cannot be used for 3 phase.
Delete

AnonymousDecember 15, 2013 at 1:05 AM

Hi Swagatam

Thanks for the
reply. I have only just come back to this after a while away and was
wondering whether you meant 50V?

Thanks -Nick
Delete

Swagatam MajumdarDecember 15, 2013 at 9:46 PM

Hi Nick,

Yes, replace the
capacitor across the relay coil with a 100uF/50 Volt.....
Delete

Reply

shahzad khanApril 19, 2014 at 5:16 PM

hi..
how are you i want to make a
project to indicate the PH of water plzz can u help me.
ReplyDelete

Replies

Swagatam MajumdarApril 20, 2014 at 9:14 AM

hi, if possible i'll surely try to
add the design soon in my blog.
Delete

Reply

Marko RadulovicMay 18, 2014 at 12:06 AM

Is this a good scheme for soft
start:
http://static.elitesecurity.org/uploads/3/2/3215883/APEX%20soft%20start.jpg

ReplyDelete

Replies

Swagatam MajumdarMay 18, 2014 at 8:38 PM

could be, but the last design in
the above article is simpler
Delete

Marko RadulovicMay 19, 2014 at 2:03 AM

can you build ponticiometar to
that scheme I sent you, and exactly where and how many ohm
Delete

Swagatam MajumdarMay 19, 2014 at 6:21 PM

there's no easy way to insert a
pot in the design, it will need to be modified greatly for that.
Delete

Marko RadulovicMay 19, 2014 at 6:32 PM

so can you change the schema with
a built-in potentiometer with labels, of course if it is not a problem for
you and thank you
Delete

Swagatam MajumdarMay 20, 2014 at 3:16 PM

the existing design is already set
at 50% less power. for a pot control feature the MOC LED will need to be
controlled through PWM using a IC555.

If possible i'll post it in
this blog soon.
Delete

Reply

Pat SelimMay 18, 2014 at 7:18 AM

Hello again Swagatam,

I
stumbled across your blog, again, when looking for a circuit allowing me to
drive an air compressor (and maybe a small fridge) from an inverter rated for
300W, with a peak of 600W. The compressor itself draws 240W, but the truck's
fuse allows for 300W, no more. Direct battery connection is impossible as it
sits below the driver's floor. Inrush current is unspecified.

Do you
know how much current would be drawn with your circuit when compressor is
started?
ReplyDelete

Replies

Swagatam MajumdarMay 18, 2014 at 9:20 PM

Hello Pat,
A soft start
feature could be initiated by suitably selecting R2 in the second circuit
however all the circuits explained in the above article are basically for
safeguarding the concerned switches and contacts from the heavy initial
surges which is implemented by diverting or sharing the current through a
triac,

Any inductive load will necessarily draw the specified amount
of current and it's quite recommended, I think you can use a slow-blow fuse
which would wait for a second and will not blow if the surge does not last
beyond that initial phase.

or may be you can try an electronic fuse
as explained
here:

http://homemadecircuitsandschematics.blogspot.in/2012/04/how-to-make-automotive-electronic-fuse.html
Delete

Pat SelimMay 22, 2014 at 8:00 AM

Hello,
I'm not sure to properly
understand what you mean by "specified amount of current". Of course I don't
expect the compressor to draw anything less than the 240W written on it,
just to eliminate very high inrush current to avoid burning the inverter. By
adapting the last circuit to account for the necessary "kick" in motors than
can't be unloaded, like in a fridge, by how much would the inrush current be
reduced?
Delete

Swagatam MajumdarMay 22, 2014 at 6:28 PM

Pat, If the motor is loaded, it
wouldn't be correct to force a soft start to it because that would cause a
choking effect on the winding and the motor would not initiate properly but
keep drawing heavy current, so it has to be allowed to suck-in the required
full amount of high inrush current, just to enable it to produce that
initial "kick" and restore into the normal stance as soon as the motor has
gained enough RPM.

The last circuit in the above article would not
stop the motor from drawing the initial high current, it just ensures that
the toggle switch is kept aloof from the initial surge and the contacts
never burn due to these inrush currents.
Delete

Reply

Marko RadulovicMay 23, 2014 at 7:52 PM

Figure 3 is a not good scheme for
electric motor immediately at full speed
ReplyDelete

Replies

Swagatam MajumdarMay 24, 2014 at 2:09 PM

why?.....first of all it's
designed for safeguarding the switch contacts not for soft
start.

however the 100uF capacitor at the triac gate could
effectively produce the required soft start also...
Delete

Reply

Marko RadulovicMay 24, 2014 at 2:18 PM

in this
scheme:
http://3.bp.blogspot.com/-62VIG17IfmA/Ul5QSpoYZFI/AAAAAAAAFgQ/jhSjl1jMmtU/s1600/motor+soft+start+circuit.png
I
traded a variety of values ​​of capacitors but nothing all the same moving at
full speed
and relay 12v very much to hear there are probably more than
12V

I can not believe that the Google can not find a scheme that works
soft start
ReplyDelete

Replies

Swagatam MajumdarMay 24, 2014 at 6:09 PM

the motor will not take 1 second
or 2 seconds to catch speed, if it does in that way it's coil could
burn.

electronics is all about understanding and then
building.

The 100 ohm resistor needs to be increased also along with
the capacitor to influence a delay.

The relay has no connection with
the delay it's the triac which causes the delay.
Delete

Reply

amieJune 10, 2014 at 11:52 AM

Hello, thank you for posting this
circuit..

for last circuit, Is that suitable for 100 to 300 Watt motor
waterpump?
Diode 4007 and Relay 12 V, what is that for in the
circuit?

Thanks
ReplyDelete

Replies

Swagatam MajumdarJune 10, 2014 at 4:38 PM

Hi, thanks, yes it would be
suitable since the triac is capable of handling well over 30
amps.

the relay is for switching the triac ON, so that the switch is
relieved from any sort of initial surge current and thus makes sure the
switch lasts forever.

the diode is for half-wave rectifying the relay
supply voltage from the 1uF capacitor.
Delete

Reply

amieJune 11, 2014 at 9:22 PM

I do understand that no more fire in
pressure switch (for my case using waterpump), because TRIAC taken that job,

But how this circuit reduce motor starting current?, As far as I can
see this circuit look no delay at all...
ReplyDelete

Replies

Swagatam MajumdarJune 12, 2014 at 10:34 AM

try the second circuit, the last
circuit is specifically intended for protecting the contactor or the switch,
it may not help in providing a slow start
Delete

Reply

amieJune 15, 2014 at 9:17 AM

Hi,..

I'm using PSpice to
simulate voltage at the gate of BTA.
I replace capacitor 100uF to 470uf,
voltage increase from 0 to 5 Volt in 1 second. Is that mean Triac output will
slowly increase from 1 to 220V in 1 Second?

I Dont know the working
principle of the triac,.. Sorry, I'm Newbie in Power Electronics...
ReplyDelete

Replies

Swagatam MajumdarJune 15, 2014 at 12:20 PM

yes it would slow down the triac
anode to cathode current but only for a very short duration, after that the
triac would instantly fire to full conduction.

You can also refer to
the following design which I posted recently, and it makes more
sense:

http://homemadecircuitsandschematics.blogspot.in/2014/06/motor-soft-start-circuit-for.html
Delete

Reply

Hector Martinez DominguezJuly 23, 2014 at 4:46 AM

Hi there, first of all I need to
congratulate your writing and your site, it is very good, so far it has helped
me quite a lot, that said I would like to make this circuit for my place, but
I have one issue.
I can't find this TRIAC anywhere, (there's not much
supply/demand for electronic components where I live), I can find smaller
TRIACS, but I don't know if they will be able to behave just like your
circuit. Do you think I could replace this TRIAC with a more modest
one?
The specifications of my motor are:
Power: 1 HP / 0.746
kW
Voltage: 127/220 V
Current: 16.9-8.1 A

Any help will be highly
appreciated, cheers!!
ReplyDelete

Replies

Swagatam MajumdarJuly 23, 2014 at 8:15 PM

Hi thanks! you could probably try
using a 10amp triac which is comparatively smaller than the shown one. A
10amp triac would hopefully handle the initial kick of a 1HP motor, moreover
the attached dimmer circuit would set the triac at around 25 to 50% less
current so it would quite fine (the second circuit in the article)
Delete

Hector Martinez DominguezJuly 26, 2014 at 9:22 PM

hey!! thanks a lot for the
response! I managed to find a BTA16-800B, hopefully it will do the trick, I
will try the second circuit in the article with this triac, and the
specificacions of the motor I posted above, hopefully it will be able to
have that initial kick, start, and don't have that pick of current.
I'll
post my results back, cheers!!!
Delete

Swagatam MajumdarJuly 27, 2014 at 1:25 PM

Hmm..BTA16-800 looks quite OK to
me since it's rated to handle at least 16amps continuously.

I
sincerely hope you succeed in achieving the intended results, wish you the
best!!
Delete

Reply

steveinatubeDecember 11, 2014 at 1:06 AM

I need a soft start for a 15 amp,
120 volt Table Saw. I think circuit 2 is what I need? what is the value of
L1? I have plenty of coils and chokes but can only identify by inductance and
size. My triac is rated for 40 amps.
ReplyDelete

Replies

Swagatam MajumdarDecember 12, 2014 at 10:26 AM

L1 is not critical, it's
introduced only for suppressing noise in radio receivers, however you can
make it yourself by winding around 200 turns of 1mm magnet wire over an iron
bolt
Delete

Reply

Bhagat NishitJune 8, 2015 at 1:37 PM

Any switch that can only ON then
OFF using any technique without switch OFF manual.
ReplyDelete

Replies

Swagatam MajumdarJune 8, 2015 at 8:13 PM

sorry, I could not understand your
need....
Delete

Reply

Naveed RasheedJune 10, 2015 at 11:19 AM

hi i want a soft starter just for 1
hp starting capacitor with clutch based motor which circuit of soft starter
should i use? can u plz tell me?
ReplyDelete

Replies

Swagatam MajumdarJune 11, 2015 at 8:04 AM

Hi Naveed, you can try the second
circuit from the above article, I would be also publishing a PWM based soft
start circuit soon, which you can refer to for your application once it gets
published
Delete

Reply

peter lewisJuly 15, 2015 at 8:43 AM

Hi Everyone,
I
have a small 6v dc motor to drive a model carossel I would love to have a
soft start or slow start, to make it look real, max amp draw would be no more
than 1 to 2 amps, nominal draw would be around 500 to 800 milliamps, does any
one have any ideas as to what I can use.
Regards Peter
ReplyDelete

Replies

Swagatam MajumdarJuly 15, 2015 at 1:36 PM

Hi Peter,

you can try the
following
concept:

http://www.homemade-circuits.com/2015/06/pwm-motor-soft-start-circuit.html
Delete

Reply

Z@h!DAugust 21, 2015 at 8:17 AM

Hi everyone,
Can i have your
e-mail? i want to discussion about my project. my project is water pump
pressure controller. i have problem to create the circuit. tq
ReplyDelete

Rea Mae kempisDecember 10, 2015 at 6:54 AM

Sir good day..sir can this ckt be
applied to a three phase motor?..if not, do you have a ckt for a three phase
motor
ReplyDelete

Replies

Swagatam MajumdarDecember 10, 2015 at 12:08 PM

Rea, for a 3 phase motor, it would
be more appropriate to incorporate a PWM based soft-start, which looks
reliable as described in the following
article:

http://www.homemade-circuits.com/2015/06/pwm-motor-soft-start-circuit.html
Delete

Reply

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Swagatam
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I am an electronic hobbyist, inventor, a
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