Tuesday, 21 January 2025

PIR Sensor Modify Field of View. Infra Red Mirror

 For the past few weeks I have been over-engineering the replacements for the security lights outside the front of my house. They are now screwed into reclaimed teak pads which should have a service life of 80 years. The cable is armoured and secured to stainless steel bases. The PIR sensors are wired together so that either sensor will light both lamps. 

The most interesting bit is the infra-red mirror in front of one of the motion sensors. The sensors have a wide field of view, but it's not quite 180 degrees. What this means is that when you approach my front door the lights will come on, but when you leave the house, you're in the sensor's blind spot and you're left in darkness until after you've tripped down the stairs.




The sensors work on infra-red emitted by warm objects. Polished aluminium will reflect infra-red radiation. I just happen to have some aluminium foil tape from another project, but the shiny side of kitchen foil should work just as well. I've put a little plate covered in foil tape in front of the sensor at 45 degrees. Instead of looking out the front, some of its field of vision is now pointing directly at the front door. The most amazing things are that 1) it works perfectly. 2) I managed to get it working without a thermal camera, so I couldn't see what it could see, or whether the tape was actually reflective in the infra-red.

Richard "Let There Be Light On The Stairs" B

Friday, 17 January 2025

Goodheart's Law

 When a metric becomes a target it ceases to be a good metric.

I discovered last year that I had put on an unwanted 5kg and I have been slowly removing it, except over the Christmas period when I put some weight back on. This year my progress has been much faster and I'm currently within 400g of my target weight.

It turns out that the easiest (but probably least productive) way to lose weight is to stop going to the gym. I usually go to a rock climbing wall twice a week, but in recent weeks I've been lucky to get there once a week. These calendar issues coincided with my most rapid weight loss. I worked out last night that I'm losing muscle rather than fat.

So it sounds like I still need to feel a little bit hungry most of the time AND do all my exercises.

Richard "Thanks I Hate It" B

Thursday, 9 January 2025

Cure Hiccups Every Time

 For about a decade I've been telling anyone who will listen that there are two different (but very similar) bows that you can tie shoe laces into. Only one of them is secure. I don't think I'm responsible, but the knowledge is becoming a lot more widespread and there are multiple web pages and videos about it.

I will now share my family's method of curing hiccups. It seems to be little known, but more effective than most.

The "patient" is issued with a glass of water. The "doctor" gives the commands "Sip!" and "Swallow!" repeatedly in a random order. When commanded to sip the patient sucks a little bit of water from the glass into their mouth (but does not swallow) even if there is already water in their mouth. When commanded to swallow the patient swallows even if their mouth is empty. This procedure continues until the glass is empty, or it's clear that the hiccups are cured, or you're both bored. It doesn't work if the doctor becomes predictable so its best for the doctor to repeatedly toss a coin as quickly as they can and shout "Sip!" for heads and "Swallow!" for tails.

Richard "it always works" B

Thursday, 2 January 2025

Bad House Guest

 I believe that one of the things that make holidays enjoyable is that you take a break from worrying about things. You're not thinking "I really must make the cable entry for the security light watertight" while you're on an Atlantic cruise.

As such I was a terrible houseguest over the Christmas period. I stayed in my friend's lodge on a holiday park in North Devon. If you're not familiar with a lodge, it's much nicer than a static caravan, but you could move it somewhere else - if you had a large crane and two lorries.

We visited his father and I gave my friend some advice about dealing with the finances of the elderly - adding massively to his New Years To Do list. I went outside in the morning and came back inside to tell him that his gutters were blocked and that the downpipe was disconnected - adding massively to our Before Lunch To Do list.

I was also partly responsible for some pretty shocking hangovers, but they seemed to appreciate the cocktails that preceded them.

Richard "ghost of chores yet to come" B