[Noisebridge-discuss] FW: Toyota

[Mitch Altman]

There's a big TV-B-Gone fan who just retired as a technician from CBS (yeah, lots of people who work in TV are TV-B-Gone fans).  He just sent me his idea of how he thinks the Toyota accelerator pedal works, and what he thinks goes wrong with this design.

 

The attached diagram is a crude sketch of how the accelerator is supposed to work (assuming attachments get through to the list). 

 

Just thought folks might be interested.

 

Mitch.


 

 
> -------- Original Message --------
> Subject: Toyota
> Date: Sat, 03 Apr 2010 21:34:01 -0400
> From: georgenann at aol.com
> To: mitch at cornfieldelectronics.com
> 
> 
> 
> Hi Mitch,
>

> Here is what I think may be in the little box connected to the gas 
> pedal. Hope you don't mind a quickly drawn diagram, I am no artist. Also 
> the terminology may not be correct, but I'm sure you will get the idea.
> For lack of a better term, the "tone wheel" can be almost any kind of 
> toothed device which can generate pulses when passed thru an 
> optocoupler, or any other type of device, IE: Hall effect stuff, etc.
> Opto coupler (A) generates pulses, no matter which way the tone wheel is 
> turned. Opto coupler (B) is 90 degrees out of phase from opto coupler 
> (A) and with either simple logic or software in the computer, will 
> generate either a high or low depending on which direction it is turned. 
> Then the computer will either count up or down, causing the engine to 
> speed up or slow down.
>

> I think the problem may be in the hi or low signal as derived from the 
> two optocouplers. If it is stuck in the hi mode, a driver could have 
> the pedal halfway down, then take his foot off and the pulses generated 
> by optocoupler (A) will still cause the computer to speed up, not slow 
> down. Any further motion of the pedal in either direction will cause 
> the engine to speed up even more.
>

> Any angular movement of either optocoupler will cause a failure of this 
> type, it could go either way, either speeding up or slowing down. The 
> problem may be from just a bad led or fototransistor in the opto 
> couplers or if the tone wheel is too small even a slight position change 
> would result in in a failure of the up/down signal. There are plugs 
> involved also.
>

> The first time I ran into this type of circuit, many years ago was in 
> the Sony BVH 1100 video tape machine. The FF/Rewind knob worked in this 
> way. When the opto couplers weren't positioned correctly all hell would 
> break loose, resulting in little bits of tape all over the place. Most 
> digital tuning on ham gear is the same type system as is the volume 
> control on most car radios nowadays. Just about all video tape machines 
> have the same thing as do some vcr's.
>

> There was some wing ding professor on TV saying that most of the 
> accidents were under power lines and they were interfering with the 
> computer, but it seems that if that were the case the speed and 
> operation of the engine would be impaired, not speeding up. Toyota has 
> come out with a fix in which a brake override was added so that if the 
> engine is going fast and you hit the brake the engine would slow down. 
> That is a good idea, but it tells me my idea may be the real culprit.
>

> I know this is just a rough description of the system as I see it, but 
> you should have no trouble doping it out.
>

> 73,
> George Keller

 		 	   		  
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