Sharp IS471F Detector

[slurp]

These Sharp sensors have been presented in a few places for opponent detection, including my inital thoughts for the cardboard 'bot, but in practice they are a little limited.

There's little to the device, they cost about £3 and are available from http://www.farnell.co.uk, they need a matched IR LED (940um) and a decoupling capacitor (0.33uF) with a power supply of 4.5 to 16V.



The LED is driven directly from the device, and the detection output can be connect directly to the controller. Care is needed to ensure that you don't have IR leakage directly from the LED to Sensor, there are a few ways of sorting the problem

Fit the LED to the underside of your circuit board, using the board as a barrier to the IR light. (Pictured below)
Use a little heat shrink to shroud the sides of the LED.



Now we hit the problem.... range! I've found that we get about 50-60mm with 4.7V supply and little more 60-70mm at 6.3V Given the size of the Dohyo you won't even see your opponent in the starting positions

Ok, maybe you've bought these already. Are they for the bin? You might be looking for something with better range when seeking out the opposition but these could be used to the rear or side of your 'bot as a little protection from attack from behind.

Yet another item for my To Do List of application sheets, to be covered in more detail but one last note... while they are billed as "impervious to external disturbing lights due to the light modulation system" they will detect light from another similar detector. While sheilding your sensor from direct IR from it's on LED you'll have do the same with any other sensors LED.

Best regards,
Colin

[slurp]

Just to prove the work arounds, and tweaks, are always out there, Gary Aylward brought "Origami" to the AWS event over the weekend using these Sharp sensors for the main opponent detection.

He drove a pair of LEDs via a transisitor switched from the GL output, giving and increased range - around 150mm. He said this solution came from a French website, hopefully I'll pick up the link later.

regards,
colin

[Gary]

http://www.the-starbearer.de/Roboter/Ba ... 1Modul.htm

This is a German site where I first found the external transistor mod. It was linked from a German robotics forum (hard going unless you can read German). The circuit diagram is self-expanatory.

I used a PNP transistor that I had to hand and two LEDs in series. I'm not sure that 2 LEDs actually give any more range though.

I have had problems with direct pick-up of the IR from the LEDs. Heatshrink sleeving over the LEDs helps, but the positioning is still quite critical.

Also, the sensors ideally need to look slightly upwards to avoid "seeing" the floor outside of the dohyo if it is light-coloured or shiny. I may modify Origami to place the opponent sensors low down looking up 10 degrees or so.

[slurp]

http://www.the-starbearer.de/Roboter/Baugruppen/IS471Modul.htm

This is a German site where I first found the external transistor mod. It was linked from a German robotics forum (hard going unless you can read German). The circuit diagram is self-expanatory.

Cheers for that... I always find this http://babelfish.altavista.com/ useful when reading foreign sites.

One funny translation on that site. Where I thought it should read "more current" it was "more river".... I don't think the river would have done much for the LED brightness

It seems they managed 160mm range, similar to what I thought you'd been getting.

I have had problems with direct pick-up of the IR from the LEDs. Heatshrink sleeving over the LEDs helps, but the positioning is still quite critical.

I've tried putting the LEDs on the opposite side of the board to the sensors, without heat shrink, this seemed to work.

I may modify Origami to place the opponent sensors low down looking up 10 degrees or so.

Getting low down seems like a good idea, especially if we see something like "BUMP" appearing... most have sensors that look right over the top. Seemed like super stealth!

regards,
colin

[Gary]

Fortunately I can read German fairly well. Babelfish always amuses me with its determined efforts at completely literal translation. In the computer age with more and more English words entering other languages it seems doomed to fail without some intelligence behind the translator.

"Strom" can mean current (of water or electricity), river, stream (of water, people, etc) or (figuratively) tide. It is related to the English "stream". It is much more common to use "Fluss" in German for river. Context is so helpful in translation work!

I am always amused that Babelfish is confused by the use of the English word "links" on German web sites. In German "Links" means "left", so it is dutifully translated by Babelfish, leaving a navigation bar with a button mysteriously labelled "Left"

[slurp]

Just noted a discussion on comp.robotics.misc and a little confusion on these sensors... a point I didn't touch on before is the Low Output on detection, most people expect a high!

regards,
colin

[slurp]

I'd seen some interesting two and three way sensors from BittyBot based upon these devices a while ago but I didn't recall the ProxDot that Jon Hylands described using on Seeker 2x.

It's a single detector mounted with two LEDs, looks like an excellent package but will require a little surface mount soldering.

regards,
colin

[JonHylands]

Just so you know, the ProxDot is REALLY small...



That's my index finger...

I use it (on the front) as a close-ir sensor only. Its not intended to replace the GP2Y0D340K sensors, but rather provide one more piece of the puzzle - "Is the opponent I am detecting really close, or not so close?"

- Jon

[slurp]

Thanks Jon,

I was just about to ask BittyBot for permission to use one of their images but your finger makes for a good comparison for size

Considering some of the other discussion it's good to know that where opponents are able to travel at high speed (1.5 m/sec) then they'll have only moved 1 mm in the time it takes this sensor to react... what we do with the signal is another problem

It appears that http://www.robotmaker.co.uk/ are suppling the ProxDot for 15 euro a pair or 26 for four. The IS471F has dropped in price at Farnell, while they're under £2 now the PCB and other components of the ProxDot... the dollar price at http://www.hvwtech.com/ is more favorable at $14 for 2 and $22 for four but I've not checked the shipping which might just tip it over the balance especially as duty may be picked up where it's not additional on European purchases.

I guess these remain a good choice when starting on your budget minisumo... they'll carry on being useful as the over all spec is improved.

regards,
colin

[slurp]

I think I'm going to use a pair of these on one of the low cost minisumo with the range boosted using a transistor arrangement like Gary's minisumo.

The old link has broken but there's a similar presentation here:

http://www.kreatives-chaos.com/artikel/ ... -mit-is471

regards,
colin

[slurp]

Before I set about tweaking old parts into new circuits I thought I'd knock this short video together:

http://www.youtube.com/watch?v=dSs1VGr_UbI

It uses the simple (data sheet) circuit and a simpler (PICaxe) flow chart program:



Flickering LEDs will be showing we're on the edge of detection, range as said before about 60-70mm but is subject to the surface reflection.... paint your 'bots black to hide from these!

regards,
colin