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Comment: Re:Doesn't solve the problem (Score 1) 136

by svirre (#48292839) Attached to: A Smart Electric Bike: Taking the Copenhagen Wheel Out For a Spin

Have you ever tried to ride with a good set of studded bicycle tires? Spinning or breaking traction really is no problem as they grip every bit as good as a studded car tire (Directly related to tire pressure), but are subject to much less sideways loading due to significantly less speed and mass.

Regarding lights, you obviously need to get a light to see by, not just a marker. Such lights are readily available and not at all a speciality item any more. (more often the problem lies in the opposite end: That lights are too powerful without enough thought to the light distribution, but light solving these issues are also easily available)

Bikes are not unstable at low speeds. It is hard to balance with NO speed (But you can just put a foot down), as long as you have any speed at all stability is good. Braking power is as good as your traction, which is very good with good studded tires. Compared to cars bikes have comparable contact area in relation to mass (Pretty much given by tire pressure)

I ride safely throughout winter and here we have ice and snow for 4-5 months every year with temperatures as low as -25C

Comment: Re:Just moves a choke point (Score 3, Informative) 395

Mangled my own text. Sorry.

Generally fast chargers will not be in constant use. Hence it is acceptable to build a battery pack in the charging station, which can charge at a more reasonable speed off the grid and be capable of delivering high current at a presumably much much less than 100% duty cycle.

This was done here:

(Apparantly slashdot chokes on the much much less than sign)

Comment: Re:Just moves a choke point (Score 2) 395


Keep in mind most EV charging can be done overnight at household outlets, only a few very long journeys will need topping up during the day, so it is reasonable that the number of fast charging outlets will be much less than current gas pumps even when EVs reach near complete market penetration, thus the number of installations will be small enough that costs will not be onerous.

Comment: Fun project but... (Score 1) 46

by svirre (#46027519) Attached to: Sniffing and Decoding NRF24L01+ and Bluetooth LE Packets For Under $30

why so much complexity to decode a standardized protocol.

Just to be clear. This is no security breach this is just a very complicated way to set up a demodulator. All that happens is that this guy pulls out the bits from the on-air datastream. Any reasonably configurable 2.4GHz band RF device capable of 1Mbit GFSK would be able to do this.

BLE uses AES to encrypt the channel, so to compromise security you need to extract the key. You either need to compromise the initial key exchange, or you need to perform a successful side channel attack. Both options are certanly viable technically. However in practice. BLE devices pair once at the start of their life and never again limiting the practical scope of a key extractioppn by key exchange comprtomise. Side channel attacks require physical access and as BLE devices tend to be in physical control of their user this is also a bit challenging.

Comment: Left as an excersise for the reader... (Score 1) 365

by svirre (#45903181) Attached to: Ask Slashdot: How Many (Electronics) Gates Is That Software Algorithm?

As a first pass you can estimate adders as 10 gates pr. bit, state as 20 gates pr. bit and multipliers as 10x bits squared (Unless it is by a power of two in which case it is free) If you need to to division in your algorithm you should redesign it. If you use floating point, everything gets huge (Try not to use floating point, remember in hardware you do not need to deal with arbitrary word size restrictions, just scale word sizes to suit the requirements)

Now, figuring out exactly what resources you need, this is where you will get into trouble. Normally you will reuse some (lots) of your arithmetic, but exactly how much depend on what performance/power/gate count target you need to hit. More reuse means less gates but faster clocks (Which can drive you to more gates if you get into trouble on timing closure). The extreme case is software which just reuse a very limited set of ALUs, the other extreme is an unrolled design where algorithmic operation have dedicated hardware, so one iteration takes one clock.

Depending on performance targets the same algorithm can have a factor 1000 difference in gate count.

Comment: High Frontier (Score 1) 87

by svirre (#45716239) Attached to: The Geekiest Game Ever Made?

Try High Frontier by Phil Eklund ( A game about industrializing space made by an actual rocket scientist.

The board is beautiful with spaces representing stable orbits and movements represented by delta-v needed to change orbits.

Rocket stacks are built by reasonably realistic technologies and fueling and mass adhere to the Tsiolkovsky rocket equation (Placed in an elegant table array for simple use)

Comment: Re:Always wondered.... (Score 2) 348

by svirre (#45716089) Attached to: Red Light Camera Use Declined In 2013 For the First Time

Some legislatures assert that the person whose name is associated with the cars license is ultimately responsible for illegal operation of the vehicle. Such legislatures usually cancel the fine if you have reported the car stolen or will reassign it if you provide information on who actually drove the car.

Comment: What about capacity (Score 1) 333

The largest issue I have with the hyperloop proposal is its rather pitiful capacity. At the highest rate proposed, with once cart every 30 seconds it still only transpoprts ~3600 PAX/hr, which is about on par with a 3 lane highway and that is before mixing in the car carriers.

Bog standard high-speed train lines do 30000 PAX/hr routinely, and while the hyperloop carts might be able to scale some, based on how they do the air bearing and that I think linked carts likely will not work, I doubt they can scale much other than by building multiple tubes (which adds upp the most expensive component in the system)

The biggest value add by public transport is to be able to free up the excessive area consumption an automobile based society incurs, but to do this the public transport in question better beat the automobile in land use with a wide margin.

Looking at speed alone is a bit of a red herring. faced with increased transport speeds people have always responded by traveling further which just escalates the problem of increased land use and increased energy use for transport. Throughput pr. unit land is likely a better metric for sustainable travel solutions than raw speed.

Comment: norway (Score 1) 452

by svirre (#44321793) Attached to: Tesla Motors May Be Having an iPhone Moment

A good chunk of tesla sales go to norway, making norway the first country outside US to get Tesla superchargers. The reason is simple: EVs have enoromus tax breaks and road access privelidges:

No VAT (Equivalent to US sales tax) Normal VAT is 25%
No taxes. Most cars get added taxes to the tune of $4000 and up. Cars in the same performance bracket as tesla usually have taxes in the $20000-$50000 range. (Taxes are based on emissions and weight)
Access to bus lanes (Which makes most EVs in norway largely concentrated in a single county just outside Oslo where the highways are notoriously congested)

These benefits will not last .If a lot of teslas outside-US buisness is based on such tax breaks I foresee a significant political risk for teslas buisness

Comment: Re:Wi-Fi toothpick (Score 1) 401

by svirre (#44022847) Attached to: Wi-Fi Light Bulbs Shipping Soon

A wifi module is unlikely to draw more than 50-80mW while active And it can likely idle a lot so the average should be able to hit 1mW. Replace the radio with something more power efficient like zigbee lighting (based on 802.15.4) and you can divide these numbers by a factor 10.

A LED module for domestic lighting would likely draw 1-10W while active, so unless it is on on a very short duty cycle the LED would dominate.

Comment: Building roads won't help (Score 0) 431

by svirre (#43551551) Attached to: Elon Musk Hates 405 Freeway Traffic, Pays Money To Speed Construction

"He who sows roads, will harvest traffic" - H.J. Vogel

Building more highways only encourages more driving, it is the congestion that will be invariant, not the traffic. It may take a a couple of years, and the congestion may move a bit, but the congestion will remain. Fundamentally building more roads is a lousy solution to the transport problem. See also "The fundamental law of road congestion: Evidence from US cities" By Duranton & Turner

Imagination is more important than knowledge. -- Albert Einstein