30 replies to this topic

[mini13]

What you could do is rig up a regulator,

something like a LM 7805 with 2 smoothing cap, (say a pair of 220nF's one on the input leg one on the out put both going to ground), with the middle pin grounded this will give 5 volts out, stick a variable resistor (or potentiometer) of around 2 k ohms on the output and connect it to the speedo, adjust the pot untill the speedo is seeing what voltage it normally would from the batery, probably 3v.

If you like i'll do a sketch tomorow.

[Tomf]

Thanks that is some very useful information dklawson

[Tomf]

Yea it would be very useful if you would be able to knock together a quick sketch for me.

[dklawson]

On my car I have the QL-5000 inside joints on the driveshafts and I was able to mount the magnet in one of those bearing cups. I made an angle iron bracket to attach the pickup to the gearbox. You'd have to do this a little differently with Pot joints but I'm sure you could make it work.

Repeating what I said earlier, do not replace the bicycle speedo battery with switched power from the car.

Another bicycle speedo brand commonly outfitted to to cars and motorcycles is Topeak. I didn't pursue their products because they cost twice the Sigmas.

I've also added some links to my last post.
To repeat them here:
http://www.geocities..._toys/bc80.html
http://www.strangely...comp/index.html
http://www.kartingte...om/tech/mph.htm

[Tomf]

Thanks there some very useful links do you know if they turn on and off automatically? i couldnt find this anywhere.

[Gazman]

Worth a look, has auto sleep

http://www.extrauk.c...Computers/7360/

[dklawson]

I'm sorry, I guess I wasn't clear earlier.

The LCD DISPLAY of a bicycle computer/speedometer turns on and off automatically but the circuitry is always running in the background. ALL bicycle computer/speedometers are literally always on. HOWEVER, what they do is automatically turn on the LCD display when they see the pickup switch turn start actuating. After a period of no activity from the pickup (3 to 5 minutes) the LCD turns off.

Don't worry. The Sigma unit will run for about 3 years on a coin cell AND they are easy to reprogram when you change the battery. If you change the cell when the display starts to dim you can write down the scale value and the odometer reading and re-enter those values when the new battery is installed. You won't lose a thing.

EDIT:
The Topeak model in the link above is one of the alternate models I mentioned in an earlier post. I hear they are a good choice but I have no experience with them. Also as I mentioned in a previous post, at least in the U.S. the Topeak models cost about twice as much as the Sigma units.

Edited by dklawson, 28 April 2007 - 03:29 AM.

[Guess-Works.com]

I find the cheap £5 halfords jobbies don't loose their memory... and provide everything you need.. however if you're planning a permanent solution I would be tempted to...

1. fit the mag pickup in the rear wheel hub
2. find a permanent live solution ( all you need is a voltage stabaliser set to return the same V as the battery, normally 3 )
3. Some form of illumination for the device...

None of that is difficult...

[Woody]

I used a sigma bike speedo on my last mini , i mounted a magnet on my inner pot joint by grinding a small flat , smothered the magnet (from an old headphone) in epoxy resin ,no need to clamp it it just sticks!
the bracket i made fron a small bit of tube and mounted under one of the diff bolts .
no need to extend the wire as sigma do a kit to mount the sensor on the rear wheel of the bike
i got rount the illumination thing by pointing a LED at it (wired to my side lights )
carefull how you measure the wheel size and input the info as i once saw nearly 200 MPH !

[Phaeton]

Alternativly you could go for a proper one that has all the warning lights attached as well.
[attachment=31698:SVA33.JPG]
My magnet is currently mounted on the wheel, which is okay unless i get a puncture, you can also buy units now that screw into your speedo drive which give far better results than reed switches.

Alan...

[Jimmyarm]

If your using it as your only (main) speedo doesnt it have to confirm to a BS or kitemark etc that says its accurate within a certain percentage ?

Where is Dan when you need him

[Tomf]

Dont think that it will need to be within a certain percentage, concidering you dont even need a speedo to pass an MOT!


On another note, i went into halfords today to see what the different speedo's were like and i brought a budget one to see what the mounting will be like and to test different ways of mounting it in my 52mm gauge, so i took apart one of my smiths amp gauges, i took all the guts out of it but to get the whole thing to fit inside i had to chop that back off, so i did this and now the electric speedo fits perfectly in place. There is 4 gapes on each side of the electric speedo so this will be good for letting light come through, so it shouldnt be very hard to get it so i can light up the gauge.

[gixxerpower]

i used to have a sigma on one of my motorbikes and it worked fine just no light.

what abput these trailtech ones. i think these are illuminated to and a lot bigger display.

http://www.dirtbikeb...Electrical.html

i might get the 'vapour' one for my car one day, it has a lot of features

Edited by gixxerpower, 28 April 2007 - 09:03 PM.

[dklawson]

There are many options such as the Topeak and Trailtech. However, please remember the title of this thread included the word "budget" and that early on TomF wanted to fit something inside a 52mm diameter gauge case. Most of the models on the link above are at least twice the cost of the Sigma units. There's nothing wrong with the other units, they just cost more.

If you remove "budget" from the scope of this thread there are many options such as the performance digital unit shown in the photo posted in the reply above. However, don't assume that the investment stops with the gauge. The sending unit mentioned above (that replaces your speedo cable) is not cheap. The M19x1 thread adapters necessary to fit the Mini are not common in the U.S. and those people I know who have bought them have spent $160 [80 GBP] for the sending unit alone. Analog aftermarket speedos from manufacturers such as VDO, AutoMeter, or Defi typically cost more than $180 [90 GBP]. So, the combined sender and gauge no longer meet the definition "budget".

If you feel a 3 year battery life isn't good enough then by all means hook up a 3 volt regulator circuit to power the unit. Personally, I'd just get something you're happy with first then address issues like that if they're a problem for you.

I certainly don't know your rules on speedometers. My Sigma is a secondary unit. My Mini has a Smiths KPH speedo and for originality reasons I want to keep it and have left it installed. However, I needed an accurate secondary speedo that could display MPH and the Sigma filled the bill. It also adds the trip meter, peak speed, and clock features. That's not bad for a budget price of around 15 GBP.

[biggav]

Dont think that it will need to be within a certain percentage, concidering you dont even need a speedo to pass an MOT!

Again, it falls in to one of those things which aren't on the MOT but are required by law, not only for telling how fast you are going but for recording the mileage of the vehicle. i'll get me book out.