System Resetting while switching OFF solenoid valve

NIKHIL VALIYA VALAPPIL

Dear sir / Madam,

I am Driving MCPS2317 (GPIO expander ,SPI interface ) using PIC18F45K22 and the GPIO pins of GPIO expander has been interfaced with ULN2803a which is connected with 24VDC coil Relay. Successfully interfaced with PIC microcontroller and MCP23s17 module. Every thing is working fine.

GPIOA and GPIOB are connected to two different ULN IC and it drives relays. The relays are connected to 24VDC solenoid vale, to control cylinder, and 24VDC indicators.

The problem is when switching off the solenoid valve the microcontroller goes reset means the all system goes to reset when switching off valve. And if continue again with cycle, ON and OFF valve by commanding from microcontroller , MCP23S17 module gets damaged after some cycle.

I did not used any other active or passive components in from microcontroller to GPIO expander to ULN and to RELAY Module. (Relay Module has diode, SHAVISON Make relay module, RELAY is Omron Make).

ULN directly drives relay as described in datasheet.

Solenoid valve details :-
MAKE : JANATICS
TYPE : DC36W
VOLTS : 24VDC
POWER : 2.5W
DUTY : 100%

Solenoid valve details :-
MAKE : JANATICS
MODEL : E12612W
VOLTS : 24VDC
POWER : 8W
DUTY : 100%

Why it is happening ? Did i made any wrong ? i read in data sheet can able to drive relay using ULN and it s current is 500ma for channel.

Regards,
Nikhil v v

over 11 years ago

Ron Michallick over 11 years ago

TI__Guru**** 164886 points

Nikhil,

Be sure the PIC has a bypass capacitor on VCC pin and any reset input line not affected by the solenoid switching. The COM pin of the ULN2803A must be connected to 24V supply.

The ULN2803A can drive 500mA/CH up to 2,500mA total per device. The biggest limiting factor is usually the power dissipation and resulting junction temperature increase. For reliability Tj should be kept less than 125C, Ideally <105C.

NIKHIL VALIYA VALAPPIL over 11 years ago in reply to Ron Michallick

Intellectual 520 points

sir,

I go through some documents related to solenoid coil operation. It tells when operating solenoid coil from relay there will be a SPIKE generate and it effect to the device also. So they mention to use Snubber circuit parallel to the solenoid valve.

Unfortunately i doesnt have not much knowledge on Snubber circuit.

Before implementing snubber in circuit i will try with your suggestion by adding one capacitor at power line of MCU and check the reset pin. And also planning to introduce diode in between mcp23s17 and uln2803 to protect mcp23s17 from reverse voltage.

The schematic has been attache with the post.

regards,

nikhil

NIKHIL VALIYA VALAPPIL over 11 years ago in reply to NIKHIL VALIYA VALAPPIL

Intellectual 520 points

Sir,

i checked the MCLR pin of PIC MCU. It fluctuating while switching OFF the valve. I checked using multimeter so i couldn't get the fluctuating graph.

regards,

nikhil

NIKHIL VALIYA VALAPPIL over 11 years ago in reply to NIKHIL VALIYA VALAPPIL

Intellectual 520 points

Sir, I added one capacitor of 10uf,50v at power line of microcontroller. But still the fluctuation or change at reset pin are there. How can i prevent this ? and does the diode IN4007 at data lines (gpio ports) prevent the further damage of gpio expander from the spike ? Im not adding diode at output lines of uln because the datasheets says it has diode at outputs. is there any other way to prevent my ic and avoid spikes from reset? regards, nikhil

Ron Michallick over 11 years ago in reply to NIKHIL VALIYA VALAPPIL

TI__Guru**** 164886 points

Nikhil,

The ULN2803A has a diode that handles the relay discharge. No GPIO diodes should be needed.

Try a capacitor on pin1 (MCLR) of the PIC.

NIKHIL VALIYA VALAPPIL over 11 years ago in reply to Ron Michallick

Intellectual 520 points

Dear Sir,

I noticed that there are diodes avail on ULN Channels. But still i getting high fluctuation to MCP23S17 and cause damage of IC. So that im considering to add diodes in between MCP to ULN Channel.

I hope this can prevent MCP IC from further damage.

kindly mention other good points from your side.

regards,

nikhil

Ron Michallick over 11 years ago in reply to NIKHIL VALIYA VALAPPIL

TI__Guru**** 164886 points

Nikhil,

Which IC is damaged, ULN or MCP?
Let me know if the diodes do not help.

NIKHIL VALIYA VALAPPIL over 11 years ago in reply to Ron Michallick

Intellectual 520 points

SIr,

MCP IC got damaged after if continue to operate solenoid valve.

regards,

nikhil

NIKHIL VALIYA VALAPPIL over 11 years ago in reply to NIKHIL VALIYA VALAPPIL

Intellectual 520 points

Sir,

Thank you for your reply.

I have added one capacitor at MCLR pin.

i hope this will make some sense in my circuit.

If adding one diode parallel to solenoid valve will it help to discharge the solenoid coils voltage?

i read it on web it helps to discharge,means act like snubber.

i will quote here if i am facing trouble.

regards,

nikhil

Interface

Interface forum

System Resetting while switching OFF solenoid valve