Pulse Generation Study: 555

I am building a simple circuit for a pulse valve I am trying to incorporate into a project at work. The valve has a cycle time of ~160 μs. The instrument I wish to attach it to already has a low speed digital I/O, but it's not capable of directly signalling the valve at that frequency.

I have a couple of solutions:

Mega expensive (500$): replace the DI with something that can signal in the high kHz.
Pros: Easy to program. Drop in replacement
Cons: $$, waste of a perfectly good DIO that could be doing real work

Middle (~40$): Micro controller. Arduino can easily pull this off.
Pros: Fast to program. Easy to package
Cons: Another interface to add.
 Need to execute very fine timing on the arduino
Seems like a waste for something so simple

Cheap (~10$): Analog Circuit
Pros: Supercheap. Simple
Cons: Takes a while. I'm not an EE or analog design expert.

I decided to base my design around a 555 timer. I still need to get the signalling worked out (if you hold the trigger pin of the 555 low (e.g. start position) it will continue to signal beyond the set time interval). For the testing, I use the arduino to trigger the 555. It turns out this is an awesome combination. By hand testing/picking a resistor-capacitor combo for the 555, I could easily get the timing right, and then using the arduino as a trigger source only required writing 7 lines of code.

Digital is cool, but analog has a lot to offer.

 Setting up the 555-arduino combo was ridiculously simple.

 Trigger signal on bottom, 555 pulse on top.

The assistant cares not for the big box.

What's the Point of a Dog?

Bayram tries to help make beer.

I have good news. If you have to ask, you probably don't need one. Don't you feel better?

It is a fair question, of course. When you get right down to it, most dogs can't or won't do much. Most of us aren't hunting game, don't have major sensory disfunction, aren't  herding cattle, or needing additional home security. That pretty much eliminates all the major uses of a dog, unless you have excess dog food laying around.

So, the purpose of a dog is largely what you make it. The purpose of a dog to to exemplify the relationship you can achieve with the dog. Dog's have their own personalities and instinctual proclivities, but within that they are quiet flexible: they can be trained, almost to the point of wanting it. They'll do what you tell them to do, if you can figure out how to communicate it through a thick doggy skull. Some have thicker skulls than others. Luck of the draw.

There are a few universals in the dog experience, one is what we here call The Presence. At first you don't notice it, then one day, your friend borrows your dog to climb Mt. Washington, or you send the dog to the kennel. You walk back into the house, maybe sit down, pour some coffee, check the email. Something mundane that you do all the time, and it dawns on you: the dog, The Presence, is missing. I have not yet put my finger on how I know the difference, besides the obvious non-dog. Even sitting here, I know the dog is here. I know because the house can't stay quite without some doggy sound: shifting during a nap, a lazy sigh, the jingle of tags, the click of nails on wood, and mysterious smells. The intent motion around the kitchen table during dinner. The soft snoring at night. It's a million tiny things that don't want to be delineated.

I also think The Presence is the reason that people get new dogs when the originals pass on.

Another universal is the fundamental dog mindset. The dog functions with a completely different cognitive mode. They live a life of patient anticipation. They're constantly watching the present for signs of the future. The best example of this how easily they're fooled when you fake throw a toy, but it manifests in other ways. Bayram winces whenever he sees the squirt gun, even when he's not about to get it. He runs to the kitchen when the oven timer goes off and runs to the window when there is a certain truck noise, indicating the immanent arrival of a delivery man. They don't seem to have vivid memories, but they are constantly internalizing the causal events around them. They want to flow with the situation, and do not see themselves as an active forces that can guide it.

Dogs also see themselves as some part of a social unit. It's pretty commonly stated that they see their family as their pack, but there's some divergences between mixed people/dog groups and packs. You're not genetically related, you're in charge of all the food, you're really good at being alpha, you sleep in different places, eat different things, one of you does virtually nothing to support the group, you tolerate interactions with other packs pretty well (if not, you've got problems!) and generally you're not too interested in breeding with each other. Your relationships is not as close and more divergent than it would be in a pack. That said, they still tend to bond with you because their constantly watching and trying to anticipate you. They know what you're doing and trying to tell them better than anyone else, because they've been staring at you for years.

Like people, the shape and pace of the relationship changes over time. If you get a puppy, you'll swing from a creature that constantly needs you and doesn't get it, to something more measured. If you go on lots of walks, you'll learn how to walk together. You'll figure out your favorite commands and one of you will forget the least used ones. You'll wrestle with the situations where you can't seem to communicate with each other. You figure out how to schedule a day so you can be home for pee breaks, and get the good kennel on speed dial.

This explains why people and their dogs seem like they are meant for each other. They're somehow in tune with each other, even if the dog appears to be orbiting the on the leash at insane speeds. (The dog knows it can get away with it!)  Same goes for the dogs that respond to commands as if by remote control. The owner and dog have spent a huge amount of time getting it straight.

We and The Dog have always fallen somewhere in the middle. He knows sit, stay, down, and no. He walks pretty well, but he randomly jumps for a sniff or a passing cyclist. He also likes to protect us...  He follows us around like it's a heavy duty. He sighs heavily whenever we leave the room and he somehow -has- to follow us. He wants to sniff whatever we're doing. He's reliable. He wants out at 0600, breakfast by 0700, a walk by 0800, out again at 1700, and dinner around 1800, followed by an evening orbiting around the couch, coping petting where he can.

There isn't really a point. It is what it is. He's here. We're here. Together.

"What happens if I feed him?"
"He poops."

Treasure!

I put on my vest so I could walk the dog. I felt something bulging in the chest pocket.

Treasure!

Namely, a Zebra F-701, two Portsmoth Brewery Matchbooks, and a reciept for donuts and coffee from March 2010.

SOPA & PIPA: Not Until They're Dead

Today is The Day to tell those in power that you do not want the SOPA and PIPA bills to be made law.

If passed, these laws would end e-business and the new economy, effectively destroying the ability to form small businesses online. They have provisions that effectively restrict Free Speech by holding ISPs and businesses accountable for the content made by others.

The laws will push the US further into recession, and further hurt our ability to compete in the global market.

These laws are being drafted with the goal of protecting businesses who have not been able to adapt to new technology. Legislation like this runs against freedom, capitalism, and the American way.

Take time to tell you representative what you think.

Modify your website/blog/page so that everyone knows. 

If you do nothing, they will probably listen to the money, and leave us all holding the bag.

Learn more about SOPA & PIPA

Contact you Congress person.

John 20:25

Among the annual rituals of adulthood (like taxes, and taking the dog to the vet), that I dearly dread is the annual safety inspection required by the Virginia State Police.

In theory, this is a wonderful idea: unsafe cars are identified, repaired, or kept off the road. Unfortunately, there are some flaws in the scheme: cars are only certifiably worthy for about 5 minutes (the time between one pays the fee and enters the vehicle, only to do some vile damage to its being). And, the inspections are carried out by mechanics for a $16 fee. Given that the hourly rate for a mechanic's time is in the range of $80-110 per hour around here, that's not exactly fair compensation for the amount of time it takes to do an inspection. To boot, a large portion of the population views their cars as mysterious appliances, so their is a huge temptation to find some problem, fail the vehicle, then offer a quote to fix the "issue".

Thus, it seems that whenever I get a vehicle inspected, someone attempts to fleece me.

The volvo was due for inspection in December. It has only been about 2000 miles since the last inspection. After a ~2 hour wait, I was called back into the shop, where the car was on the lift. A large group of mechanics eagerly pointed out that the control arm strut rod bushings were loose, and the ball joint boot was torn. "It's warn out!" one proclaimed. He jammed a bar in the suspension, to show flex. I argued that the ball joint didn't knock and that the control arms weren't going to fall off, being held in by freaking huge bolts. "No! It's very dangerous! You should have it fixed right away! The wheel could fall off!" the chorus intoned. I was handed a quote for $1200 to replace the control arms and ball joints along with a failing sticker.

I purchased the Volvo 740 for $400, approximately its worth on the scrap metal market, and put in significant effort to make it road worthy. Every expense is carefully weighed against the possibility of replacing it with a car that has not been driven around the planet 15 times. I got home, pulled out the shop manual, and started looking online for parts prices. The shops quote included two ball joints for $160 ($80 each), and two control arms at $410.78 ($205.39 each). Also was 6 hours of wrench time, billed in 10 minute increments ($630). With a quote like that, I felt doomed to a lot of time under the car, on the ground, outside in January. Fun times. Worse, that kind of parts cost was going to take a bite out of the budget.

Inspecting the manual, and backing it up with some googleing, the job appeared to be doable in the driveway. Discounting the lugnuts, each side is a 6 bolt job. There is one trick: seperating the balljoint from the control arm, which are held together by a conical stud in bimetal joint. (iron stud in an aluminum control arm). It looked like a 2 or 3 hour job at worse. I figured it might take an hour to beat the ball joint out of the control arm. (I would be very wrong on this point). The manual also noted that the maximum ball joint play allowable is 1/10 of an inch.

The price of the ball joints online (from rockauto and ipdusa) hovered in the 10-20$ range. Control arms, on the other hand, were almost impossible to find. I'd have to convert the whole front end suspension to use european cast iron control arms, which use different radius rods and anti-sway linkages. From the manual, it was pretty obvious that the bushing in the control arm were meant to be replaced, the control arm is a fixture, not a consumable. I took a quick glance under the car to survey the bushings. Only the ones on the end of the control arm strut rods were notably worn. They were also designed to be replaced without the aide of a hydraulic press. How much do those bushings cost? IPD: $3. I called the local autostore. They had a set for $24, and the ball joint for $10. I took the kaboodle, and ordered another set from IPD. To recap, I spent about $65 for parts to do the same job the shop quoted $570 for.


The strut rod bushing turned out to be as easy as I imagined. Remove the wheel, remove the bolt on the front of the strut rod, remove the bolt on the frame, smack the rod out with a mallet, replace the bushings, and rebolt. The bushings are surprisingly complex... there is an inner metal shaft the follows the strut arm, an outer metal shaft that follows the control arm, and a connical metal disc that matches the cone in the control arm. All three pieces are linked with rubber to provide a little flex. Over time, the link between the inner and outer shaft gets broken apart, and the increased play allows the other parts to get chewed apart by the control arm.

Volvo 740 control arm strut (also called "radius") rod.

How the bushings are situated in the control arm.

 New and worn bushings, control arm side.

Comparison between new and worn bushings.

Control arm strut rod bushings, outside. Not the breaks between the different metal disks on the worn bushing.

Control arm without strut rod installed.

Control arm with strut rod installed.

The ball joint proved to be a somewhat different story. I removed the tire, unbolted the lower control arm link, removed the bolt from ball joint stud, and gave the control arm some tentative pulls. It was totally stuck, and totally had less than 1/10 of an inch of play. I foolishly decided to press on, given that I now had all the parts to do the job laying around in shopping bags, and it was a warm sunny day in January. (The girly would later suggest that getting the car inspected elsewhere might have been a better, less laborious option.)

I pulled my shiney new pickle fork ("ball joint seperator") out of the tool bag, carefully placed it between the control arm and the ball joint, and smacked it in with my deadblow mallet. When it felt nice and firm, I leaned on it as hard as I could, only to feel it give and pop back out. A bad sign. I did that several more times, smacked the control arm several times, sprayed the whole thing with Buster Loose, and went inside to drink coffee and wonder what I had gotten myself into.

An hour later, reapplication of the mallet and the pickle bar showed no progress. I could jam it in harder, and then fit the jack handle over the pickle fork handle, but that only resulted in bending the pickle fork. Clearly, a different approach was needed. I found this article, and thus transpired to get my own gear puller. What a clean solution!

Hardly.

I installed the puller, and started working drive screw with the ratched. I felt the tension build, and eagerly awaited the pop and control arm sag that would happen when the ball joint gave way. At some point the ratchet wouldn't move anymore. I had to get a bigger wrench. A bad sign.

What was all that torque doing? Not moving the ball joint. Just deforming the stud.

Well, damn.

Clearly, I needed to put more force on it.

I put on my bad idea shorts and started dancing.

 I braced the control arm against the bottom of the with a nylon strap, then put the jack head against the ball joint stud. Certainly, 4 tonnes of force would push the stud out. Right?

Wrong.

 Although I could get the jack handle to bend pretty far.

I bought a torch and a bottle of mapp gas, heated the joint, and slugged it with the mallet more. No luck. I ultimately pulled out the control arm, and took it to my friendly neighborhood volvo shop.

Who removed it so easily that they did not even charge me for it!

I thought they would have used a hydraulic press, the marks on the side of the arm suggest a bench vice and a sledge hammer were at play. Kudos. I don't have those.

After two days of torment, I re-assembled the front end in about 20 minutes. I cleaned the inside of the control arm off with naval jelly, and applied a thin film of antisieze compound, on the off chance it has to be removed again in the future.



I'll take it back to get re-inspected this week.

Draining the pool you take with you

The chevoldsmobuiac had an annoying habit of collecting water in the trunk. We were never able to completely ascertain the exact source, as the water did not always appear after a rain storm. In fact, interseasonal periods seemed to make the problem get worse.

My theory is that the trunk temperature would lag that of the ambient air, and water would condense, run down the sides, and accumulate in the spare tire well. This had the unfortunate side effect of making the car smell like a moldy swamp. Also added was the sound of water sloshing around in the back when executing maneuvers.

My solution to this problem was incredibly unscientific.

I drilled two holes at the lowest point of the floor pan, then painted them with rustoleum.

No more water in the trunk!

Now, if I could just replace the window seals to keep it from getting into the doors...

Can't Keep Up

Between the new job and everything else, it seems like I'm chronically behind actually looking at photos. I'm taking few photos too... there's less to see in the sterility of NoVa, to be honest. I'm thinking of trying to do more portraits. Those are harder to pull off, though generally worth it.

Besides, I think I need to find a new direction to take my art. Weeding through thousands of photos, I have a nagging sensation that I keep taking the same photos all over again. In a way, it's comfortable, like how you share the same stories with friends time and time again, but there's always a need for new material. You don't want conversations to run dry. New angles keep things fresh.

An upshot of being so damn behind is that the Ubiquitous You get to see summer in January. Too bad it's not yet bitterly cold enough to really inspire you to wish it was summer yet.

I even wore shorts today.

Here's a bunch of Blackeyed Susans to warm you eyes.

From July until October we watched a the nieghbors hibiscus plant proceed on a daily march, blooming one flower at a time, which then collapsed and turned into a wrinkled, fleshy wad.

Miniature onions do well here.

I drove home in a driving rainstorm. By the time I got inside, the sun was beaming through the back windows, though the pouring continued. I grabbed my camera and ran out into the street, just in time to see my world cast in jewels.

 Another long windy road in our old car.

This car seems out of place.

Rocks are just little rocks glued together with littler rocks.

What God Hath Wrought...

...is surreal and subject to interpretation.

Fingerprints of time are everywhere.

Irony.

Dog days of summer.

The dog equivalent of a bikini.

Another missed connection in the big city.

The girly. Beautiful as ever.