CENTER TWP — A man is accused of rigging a booby trap device possibly designed to injure his girlfriend who obtained a protective order evicting him from their home on Unionville Road, state police said.

Kenneth G. Robinson, 47, on Monday fashioned the contraption out of a board of nails connected by a string to a door intended as a kind of trip wire, said Trooper Craig Johnson.

But his girlfriend, 42-year-old Jeannie Summers, discovered the alleged “trap” before it was activated, and was not hurt.

“It had the potential to injure anyone who may have unlocked or kicked in the door,” Johnson said of the purported booby trap.

Police arrested Robinson on felony assault and other charges. He is in Butler County Prison on $25,000 bail.

Authorities said county sheriff’s deputies Monday went to the defendant’s workplace and served him with the temporary protection from abuse order that Summers had obtained earlier that day. She alleged that Robinson on Sept. 5 attacked her and threatened to kill her.

Deputies informed Robinson that the “no contact” court order barred him from the house where he and his girlfriend had lived for about three years.

But Summers was advised that her boyfriend would not turn over the keys to his house, where he had changed the locks, documents said.

Later, when she went to the house, she found the doors locked. She told police that she climbed through an unlocked second-story window to get into the home.

In the living room, Summers noticed a 12-gauge shotgun on the back of the couch. She said she had never seen the gun before.

According to court documents, the woman knew her boyfriend was prohibited by state law of possessing any firearm because of a prior felony conviction.

But in addition to the gun, she spotted a string attached to the inside of the rear door. She followed the string to a piece of plywood partially secured to the ceiling. The board, which contained 22 nails driven through it, was painted black and pointed down from the ceiling.

“A line ran from the base of one of the nails through a fastener on top of the door, down to the door knob where it was wrapped secure,” Johnson said.

The trooper checked the device, after police were alerted to it, and found that it worked.

The board swung down, he said, and the pointed end of the nails — each around 3 inches long — hit the door about 5 and 6 feet from the floor.

“It was not terribly sophisticated,” Johnson admitted, “but it did work.”

Police that night interviewed Robinson at the barracks.

He claimed he set the alleged trap and got the gun as a “form of security and self-protection” after he believed someone tried to break into the house, documents said.

Johnson would not dismiss the suspect’s claims.

“It’s possible,” the trooper acknowledged. “I can’t rule it out.”

A preliminary hearing for Robinson, who is charged with aggravated assault, illegal possession of a firearm, reckless endangerment and simple assault, will be held Sept. 24.