Basic stamp 2 with TIP 120

Borna

Hello all,
I am very new to MC and need help
I am trying to drive a solenoid with Basic Stamp 2 using TIP 120 transistor
Here is my diagram and code
As you can see the code is very simple. All I want to at this point is to activate the solenoid 10 sec

' {$PBASIC 2.5}
' {$STAMP BS2}
HIGH 7
SLEEP 10000
LOW 7

what happen is at the start of the program, the solenoid will become active for about 3 secs then become deactivated for a fraction of a sec and immediately become active again for about 3 sec, and follow the same pattern continuously

The following code doesn't do anything
' {$PBASIC 2.5}
' {$STAMP BS2}
LOW 7
SLEEP 10000
HIGH 7

The following code behaves like the first scenario
' {$PBASIC 2.5}
' {$STAMP BS2}
HIGH 7

Borna

I forgot the attachment

PJAllen

SLEEP 10000??

Try PAUSE 10000

HIGH 7
PAUSE 10000
LOW 7
PAUSE 3000

PJAllen

bonkbonk:
  HIGH 7
  PAUSE 2500
  LOW 7
  PAUSE 2500

GOTO bonkbonk

DO
  HIGH 7
  PAUSE 2500
  LOW 7
  PAUSE 2500
LOOP

72sonett

No flyback diode over the solenoid?

erco

Batteries low? Solenoids pull lots of current and the battery voltage drops over 3 seconds, Stamp resents. Try a bigger system battery or a seperate battery for the Stamp.

Also, your 1K base resistor may be too high. Try 330 ohms.

Borna

thank you all.
The issue was sleep instead of pause.
Changed that to pause and working fine.
No sure why I used sleep?
maybe I was thinking Java

Would you also tell me if the diagram looks correct?
As mentioned, do I need a diode between Pin 7 and the resistor?

erco

You should put a flyback diode across (in parallel with) your solenoid. Reverse-biased, so no current flows through it when the solenoid is energized. Doesn't do anything obvious, except when your switch off your solenoid, a huge (many thousand volts, likely) voltage spike is produced as the magnetic field collapses. That voltage spike can damage your I/O pin, but the diode absorbs that energy to protect your Stamp. You can use a rectifier diode (1N4001 type) or signal diode (1N914 type). Always good practice to add such a diode on relay coils and especially a huge solenoid coil such as you have.

http://en.wikipedia.org/wiki/Flyback_diode