Is your dog getting along a bit in years? Liking a nice warm spot to sleep? We live in a temperate region at an elevation of about 1000 metres. It rarely gets below freezing in winter, so full home heating is not everywhere. We get by with a wood heater in the living room.  The bedroom can get cold at night in winter, late autumn and early spring.

Lucy is a cross Kelpie Labrador who serves as both pet and working dog on our small mostly hobby farm. She looks after her humans, herds our cattle,and keeps feral rabbits in check. She is 10 years old now. Going a bit grey, but still quick. A kelpie is a breed of Australian working dog, good with sheep and cattle.  She is completely house trained, and sleeps on an old couch in our bedroom.

This project is pretty easy to make. No complicated microcontrollers, no software, no complex wood joints, no metal welding. Construction can be varied to suit your pet size and current bedding.

The basic idea is a light hinging frame that goes over an existing bed. The current frame is made from 3 pieces of 25mm PVC electrical conduit, and a couple of 90 degree elbows.  A low wattage 12V electric blanket intended as a car lap warmer drapes over the frame.  A light woollen blanket goes over the electric blanket. It drapes down to meet the couch at the sides. I think this was originally an airline cabin blanket. It came with the farm.  The blankets clip to the frame using 4 or 5 clips made from old PVC cold water pipe, cut maybe 4cm long and slitted one side. Something that can come off to wash the blanket occasionally. 

The frame is supported at back on two screws allowing the front to lift up.  At front, a piece of string supports things. This allows the dog to lift the frame to get in and out.  It can also be tied up for summer if desired.

That frame pivots at the back, and is free to lift at the front. I originally made a complicated, heavy wooden frame that went over the back of the couch. That didn't work. I cut much of the old frame away leaving only a rail at the couch back and somewhere to tie a string at the top.  An alternate design just uses a piece of plywood poked down behind the couch cushion. 

 I made the frame 23cm above the couch at the front, 67cm wide and 68cm deep. The depth should be a little less than the couch seat. Lucy is a medium sized dog, about 22Kg, or just under 50lb for those using archaic English weight measurements. Adjust measurements to suit your pet. 

The electric blanket came with a switch / timer thing moulded into the lead. It had to be turned on, and would only run for a couple of hours without intervention. Not pet friendly. I cut the controller off, added a couple of Anderson power-pole connectors to an extension lead from some old 2 wire house wiring, which goes under a rug to a power supply. I powered it experimentally with a think I put together from an ancient power supply enclosure holding an Ali-express power supply module and switcher. Experiments showed a single blanket worked nicely at 6 or 7 volts, 3A, 20W. That makes the nest warm, with no risks of fires or cooked or electrocuted dog. I would recommend an adjustable voltage supply with a current limit. A variable supply rated 10V or more max and 5A would be great for 1 blanket. 14V works for me for 2 in series.  Don't use a mains powered blanket, some dogs chew.  The photo shows my supply running 2 blankets in series. We minded another older dog for a few weeks last winter. Hence the plywood version.

Running at 20W for 8h a night is less than 1kW-h per month. Depending on what you pay for electricity that could be a dollar for the winter.  Hardly a massive outlay for a senior pet.

Lucy has used that couch all her life, the heated part was added a couple of years ago. It was tied up for the first few days after fitting , then the string extended a bit at a time to give her time to get used to it. Now...