How to tell if TIP120 is shot?
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I misread a motor spec and wound up sending about 6amps through a
TIP120 which was being driven by a BS1 using PWM. The stamp reset,
although the power supply was capable of delivering much more than
6amps (at 12v. I'm using an ATX PC Power supply with the necessary
jumpers and pre-loading resistors in place.).
Anyway, I caught my mistake and put a power resistor in series with
the motor to limit current to about 1.5amps. The problem is that the
stamp continued to reset periodically.
I then added an additional flyback diode in parallel with the motor
(even though the tip already has one). Fewer resets, but they still
occured.
I then added a 0.1uf cap on the stamp power pin. Still fewer resets,
but they continued.
Lastly, I changed out the TIP120 and the problem seems to be fixed.
Could I have blown something in the TIP during my first mistake that
caused the TIP to appear to function properly but continued to cause
the resets? The motor is a Radio Shack hobby motor (9-18v at 1.9amp
max).
Thanks in advance for any suggestions.
Rob
TIP120 which was being driven by a BS1 using PWM. The stamp reset,
although the power supply was capable of delivering much more than
6amps (at 12v. I'm using an ATX PC Power supply with the necessary
jumpers and pre-loading resistors in place.).
Anyway, I caught my mistake and put a power resistor in series with
the motor to limit current to about 1.5amps. The problem is that the
stamp continued to reset periodically.
I then added an additional flyback diode in parallel with the motor
(even though the tip already has one). Fewer resets, but they still
occured.
I then added a 0.1uf cap on the stamp power pin. Still fewer resets,
but they continued.
Lastly, I changed out the TIP120 and the problem seems to be fixed.
Could I have blown something in the TIP during my first mistake that
caused the TIP to appear to function properly but continued to cause
the resets? The motor is a Radio Shack hobby motor (9-18v at 1.9amp
max).
Thanks in advance for any suggestions.
Rob
Comments
will.lynelle@v... writes:
> Rob,
> one thing you did not mention is whether you added a bias resistor
> between the stamp and the TIP120, I'm definitely not an expert but I think
> you need something to prevent the transistor from pulling to much current
> from your I/O pin. Perhaps someone with more knowledge on this subject
> could explain it for both of us???
I am running five TIP122 in a control circuit. I have a 1K resistor between
the Stamp line and the base, and I have observed no problems. The TIP has a
8K resistor on the input transistor between base and emitter and another 120
ohm resistor from there to ground. This gives me about 4.4VDC on the base, and
since the TIP has a gain of 1000 I would expect the base current to be rather
low. Hope I'm right !!!
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
one thing you did not mention is whether you added a bias resistor
between the stamp and the TIP120, I'm definitely not an expert but I think
you need something to prevent the transistor from pulling to much current
from your I/O pin. Perhaps someone with more knowledge on this subject
could explain it for both of us???
Will
Original Message
From: "rrothe64" <rrothe@m...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, May 30, 2004 6:14 AM
Subject: [noparse][[/noparse]basicstamps] How to tell if TIP120 is shot?
> I misread a motor spec and wound up sending about 6amps through a
> TIP120 which was being driven by a BS1 using PWM. The stamp reset,
> although the power supply was capable of delivering much more than
> 6amps (at 12v. I'm using an ATX PC Power supply with the necessary
> jumpers and pre-loading resistors in place.).
>
> Anyway, I caught my mistake and put a power resistor in series with
> the motor to limit current to about 1.5amps. The problem is that the
> stamp continued to reset periodically.
>
> I then added an additional flyback diode in parallel with the motor
> (even though the tip already has one). Fewer resets, but they still
> occured.
>
> I then added a 0.1uf cap on the stamp power pin. Still fewer resets,
> but they continued.
>
> Lastly, I changed out the TIP120 and the problem seems to be fixed.
>
> Could I have blown something in the TIP during my first mistake that
> caused the TIP to appear to function properly but continued to cause
> the resets? The motor is a Radio Shack hobby motor (9-18v at 1.9amp
> max).
>
> Thanks in advance for any suggestions.
>
> Rob
>
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
> Yahoo! Groups Links
>
>
>
>
>
>
The only other things in the circuit are three push buttons and a
couple of status LEDs.
Rob
--- In basicstamps@yahoogroups.com, "William Pollock"
<will.lynelle@v...> wrote:
> Rob,
> one thing you did not mention is whether you added a bias
resistor
> between the stamp and the TIP120, I'm definitely not an expert but
I think
> you need something to prevent the transistor from pulling to much
current
> from your I/O pin. Perhaps someone with more knowledge on this
subject
> could explain it for both of us???
>
> Will
>
Original Message
> From: "rrothe64" <rrothe@m...>
> To: <basicstamps@yahoogroups.com>
> Sent: Sunday, May 30, 2004 6:14 AM
> Subject: [noparse][[/noparse]basicstamps] How to tell if TIP120 is shot?
>
>
> > I misread a motor spec and wound up sending about 6amps through a
> > TIP120 which was being driven by a BS1 using PWM. The stamp
reset,
> > although the power supply was capable of delivering much more than
> > 6amps (at 12v. I'm using an ATX PC Power supply with the
necessary
> > jumpers and pre-loading resistors in place.).
> >
> > Anyway, I caught my mistake and put a power resistor in series
with
> > the motor to limit current to about 1.5amps. The problem is that
the
> > stamp continued to reset periodically.
> >
> > I then added an additional flyback diode in parallel with the
motor
> > (even though the tip already has one). Fewer resets, but they
still
> > occured.
> >
> > I then added a 0.1uf cap on the stamp power pin. Still fewer
resets,
> > but they continued.
> >
> > Lastly, I changed out the TIP120 and the problem seems to be
fixed.
> >
> > Could I have blown something in the TIP during my first mistake
that
> > caused the TIP to appear to function properly but continued to
cause
> > the resets? The motor is a Radio Shack hobby motor (9-18v at
1.9amp
> > max).
> >
> > Thanks in advance for any suggestions.
> >
> > Rob
> >
> >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
the TIP -- only when the motor is attached and only when I use the
TIP that I over-amped.
Even with a new TIP, the stamp will reset if I don't put a small cap
on the power pin. I'm thinking of using the power supply's 12v and
regulating it to 5v directly on the stamp or through a 7805.
Currently, I'm using both the 5v and 12v lines of the power supply.
I have everything working now, I was just wondering if anyone else
had any experiences with TIP120's where they semi-worked after
stressing them beyond their specs.
Regards,
Rob
--- In basicstamps@yahoogroups.com, Newzed@a... wrote:
> In a message dated 5/30/2004 3:44:03 PM Eastern Daylight Time,
> will.lynelle@v... writes:
>
>
> > Rob,
> > one thing you did not mention is whether you added a bias
resistor
> > between the stamp and the TIP120, I'm definitely not an expert
but I think
> > you need something to prevent the transistor from pulling to much
current
> > from your I/O pin. Perhaps someone with more knowledge on this
subject
> > could explain it for both of us???
>
> I am running five TIP122 in a control circuit. I have a 1K
resistor between
> the Stamp line and the base, and I have observed no problems. The
TIP has a
> 8K resistor on the input transistor between base and emitter and
another 120
> ohm resistor from there to ground. This gives me about 4.4VDC on
the base, and
> since the TIP has a gain of 1000 I would expect the base current to
be rather
> low. Hope I'm right !!!
>
> Sid
>
>
>
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]