Bike rescue

It was supposed to rain, so I was driving to work, saw this out in someone’s trash, and it followed me home. $45 in parts from the Broadway Bicycle School, plus new bearings for the headset, and it’s a bike again.

I have no idea what is going on with the paint job.

Big Dummy

Front fork was aging fast on the old bike, my brother said his Big Dummy was great, I didn’t get laid off this spring, and the stock is up on solid acquisition rumors. So I bought myself a Big Dummy.

Lighting control circuit, fixed, working.

When I finally tested this circuit on a real bike connected to a real hub, it didn’t work right. I got light, but it was flickery when slow, and I seemed to notice a little more drag (this had to be in my head) than the old 350mA system, and more important, the system voltage never made it above 9 volts; no chance of charging standlight batteries using this design as a starting point. The discrepanies from the plan (too much power to lights at lower speeds) pulled too much current from the hub, so it did not run in the more efficient mode.

I figured out the difference between the model and reality, tweaked the model, and then it tracked observations. With that, I could test a fix before soldering it in, and it worked just fine.

Not so grand plans

I decided, that the next circuit I build, will do one thing well, and I’ll worry about the rest later.

More PCBs

There’s a learning curve. I think I’m past it.

Lighting control circuit, this time for sure

Every system is a second system, or so it seems.

---

Update: it really, really helps to use the right chip. After being incredibly careful about every orientation of every weird transistor, I designed the board around a “LM387N”, which is not the chip I intended or the one that I had ordered — LM258 (usually referred to as LM358, but the 258 works in the cold). I was testing the board before putting on the big components, and it was just not working, and in the end, it seemed like the op-amp was on drugs. In the end, I got out a magnifying glass to check the label. DOH!

All is not lost, but the board needs to be rerouted. I’ll sort out the pins and test again.

---

Up-update: After installing a pin-scrambler, it works roughly as predicted. The most important part of the circuit, the high-end shunt control, delivers 3.85 volts to the base of the shunt transistor at 31.1 volts. This is a perhaps a half-volt earlier than planned, but it’s a half-volt to the safe side. In the high 20s, the shunt is not activated, as planned.

Anomalies:

(1) the LED control sends a little more power to the lights than I had planned. Not lots, and it’s mostly a low-end effect. At 31.1, the control voltage is 1.7, which is exactly on target. At 22.5 it is 2.6 (plan, 3.1) and at 12.9 it is 3.24 (plan, 3.6) and at 9.6 it is 3.4 (plan, 3.8).

(2) the off-level shunt base voltage is 0.6, where the plan was 0.2. This should not be an issue with the particular Darlington shunt transistor; it claims to have a Vbe of 2.8 volts.

Further adventures in bike-light-ology

Today’s lesson: Hub generators are current sources.

Some assembly required, batteries not included

A dynamo-or-battery-driven set of lights for a bike — 200 lumens white to the front, amber low beams and running light, and a red-orange tail-light. It’s about a 3-watt system, using mostly-latest LEDs from CREE (white) and Luxeon (amber and red-orange).

Santa Bike

Bikes win for delivering packages to the post office, at least until everybody does it and I can no longer park the bike right in front.

Quick circuit for LED “high beams”

his has come up twice in the last week; I want high/lo beams, and I think Wiley needs them too. Different reasons — I don’t want to be rude to peds and other bikers, and Wiley (I think) just needs to conserve power.