Solenid driver ?

Siri

I am driving a solenoid (15V) using BS2sx using a high voltage open collector 7407 buffer IC and a a MOSFET IRF510 pulled high as shown in the attached circuit diagram.
My question is whwther the solenoid is suppose to be energised as soon as the power(15V) is connected or is it suppose to be switched on after· the BS2 command.
These are some of the readings obtained just only the power connected to the solenoid circuit.
1.across - the solenoid coil - 15.1 V
2.across - IRF 510 a) Source & Drain = 0 V
··························· b) Source & Gate· = 15 V
····························c) Drain & Gate = 15 V
When an LED ia connected with series resister the LED lights as soon as the power is on.

Is there something wrong or is it normal tohave power on to the solenoid prior to BS2 swithes it off.

Iwould like to have the power off untill the BS2 command powers the solenoid.

Help me to understant this and achive my intended goal.

Thanks

Siri
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pwillard

My Guess.· Invert your code logic and/or replace the 7407 with a 7406.

Chris Savage

Hello,

There are several issues with your circuit. First of all the MOSFET looks like an N-Channel MOSFET. If so the pull-up resistor should actually be a pull-down resistor to ground. Also, the BASIC Stamp pin can directly drive the MOSFET gate. Using the 7406 you’re inverting the signal.

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Chris Savage
Parallax Tech Support

Siri

Thanks Chris and pwillard,

I will try your sugesstions.Not using the 7406/7 and driving the MOSFET gate directly from the Basic Stamp can reclaim some real estate on the board too.

Siri

Chris Savage

Don’t forget the pull-down resistor…The BASIC Stamp pins can be Hi-Z before being initialized, however the 7406 doesn’t have tri-state outputs so you’re not doing anything with it anyway. It would always drive the line, still I would remove it. Take care.

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Chris Savage
Parallax Tech Support

Siri

Thank for all your advise - all of you are doing great job in helping people like me who are tinkering with electronics and learning while doing it.

Siri

Chris Savage

In re-reading my post I realized that could sound confusing, so I just wanted to make sure you knew you could connect the BASIC Stamp I/O pins directly to the MOSFET gates and each gate should have a 10K pull-down to ground. Take care.

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Chris Savage
Parallax Tech Support