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Simple relay controler Idea.
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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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All good suggestions, but I dont like using receiver batteries myself..

Just another thing to go flat, come loose, get left switched off (or on until its flat) or fail in some other mysterious way at a critical time..

BEC's can be a pain to isolate from motor noise and whatnot, a decent filtering circuit takes a bit of fiddling to setup - but once you've got it right, it generally stays right, unlike an Rx battery..

But Batteries are an easy way to help with a lot of radio problems Smile
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Post Mon Feb 21, 2005 9:56 am 
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Glen
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ive come up with a few ways to get around the rx batt blues.

first i just have a seperate micro in cobras bolt switch that turns on the rx batteries before the main power. so if you want to turn the robot on the radio has to be on as well..

and as for flatness cobra runs 4x 2700mah nimh AAs and kang 4x 1200mah drill nicads and ive got little charging jacks for them so i can top them up.

however i noticed that duracells last forever as rx batteries..
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Post Mon Feb 21, 2005 5:28 pm 
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Knightrous
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quote:
however i noticed that duracells last forever as rx batteries..


When I use to race my RC car in Mackay, I use to run a brand new pair of duracells or energisers flat after only 4 batteries through my car! I think I was getting jibbed Evil or Very Mad
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Post Mon Feb 21, 2005 8:48 pm 
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ffej
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Joined: 22 Jun 2004
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You would have been using at least one servo for stearing . . . I'd say that would have been taking a fair bit of current to sustain . . .
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Post Mon Feb 21, 2005 8:52 pm 
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kkeerroo
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Joined: 17 Jun 2004
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Location: Brisbane


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Most people who use receiver batteries are using them to run servos for servo switching. This means that the servos spend a lot of the time stalled while pressed against micro switches. Of course the batteries arn't going to last long Rolling Eyes .
Microcontrollers and opto-couplers and other solid-state componants draw relativly little current compared to servos and I find that my receiver batteries will last an extremely long time. 2 or 3 comps usually.
I just think that for beginers who are just starting out in electronics would benifit greatly in using a "simple" power supply rather than going into impulse response equations and fourier transforms needed to design a half decent BEC.
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Post Mon Feb 21, 2005 9:21 pm 
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dyrodium
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Joined: 24 Aug 2004
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Hey, i found this;
http://www.vision.net.au/~timotsc/elecswch.pdf
And also, i bought a basic stamp serial port programmer fron dickies for $2 (sale). Would it be at all usefull? Very Happy
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Post Fri Mar 04, 2005 7:09 pm 
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Spockie-Tech
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Location: Melbourne, Australia


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Looks OK, But its a bit over complicated to my eyes, given that a single 8-pin $4 PicAxe Micro can replace all of the circuitry in that design, and do it better..

The PicAxe can add Hysteresis (dont ask unless you *really* want to know - its complicated, google it if you want to know why its good), and Failsafe - which is essential for a bot. That circuit has neither and is much more complicated to build.

Of course the PicAxe requires that you make(or buy - they're cheap) a very simple 3-wire programming cable to connect to your PC, which may put some people off.. but you can always ask Aaron or myself, or anyone else (Jake ?) to program it for you..

The Basic Stamp is a nice microcontroller, but they are very expensive ($50+ IIRC) for very little extra functionality over a PicAxe (IMO).

And no, I'm not a PicAxe sales agent in disguise, I just happen to think they are the most cost effectinve, easiest-to-use, most powerful little single chip Micro's I've ever seen, and believe me, I've been through plenty..

(68705, Z8, Pic1684, Atmel PowerBoard, Basic Stamps, and thats just some of the micro*controllers*, which are seperate to to Micro*processors*)
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Post Fri Mar 04, 2005 8:50 pm 
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Totaly_Recycled
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Just talking about relay controlers.
My home made speedos melted a brush holder the other day and i dint have a replacement so i sat and had a bit of a think and ripped the rotary switch off and aded two drill fetts a couple of resistors and caps and now have them switching relays and still have the pwm control as well i just need to do a bit more fiddeling to get the zero point set at the right place but hopefully replaceing the servo pot with a couple of resistors should fix it .

Post Fri Mar 04, 2005 9:58 pm 
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bigjimmy



Joined: 18 Jun 2004
Posts: 40
Location: New South Wales


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I built spokie's relay controller a while ago, its a great little thing, never had any problems with it (exept when i shorted one of the outputs to the +5v rail and killed one of the outputs) It has 6 relay channels (2 weapon), failsafe, 30A handeling (could put 60A realays but drill motors dont need it.)

So if anyone wants a cheap ass controller and have a bit of electronics skills (soldering, bit of general knowledge) i suggest you build it.

The only thing is that you either have to design a pcb, or build it on a piece of breadboard. (I had to desgin the pcb, dont like breadbord)

I think I built the entire thing for about $45.

Post Sun Mar 06, 2005 5:32 pm 
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Ali



Joined: 06 Mar 2005
Posts: 92
Location: Scotland


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Any of this good ?
http://www.bobblick.com/techref/projects/hbridge/hbridge.html
http://www.bobblick.com/techref/projects/sv2pwm/sv2pwm.html
http://www.bobblick.com/techref/projects/sv2hb/sv2hb.html
http://www.bobblick.com/techref/projects/picprog/picprog.html

Ali
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Post Mon Mar 07, 2005 12:15 am 
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Spockie-Tech
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Sorry, but not really.. I've checked those pages out before.. they are good to illustrate the basic principles of a speed controller, but you'll notice that Bob clearly states that it has never actually been used in combat applications..

5 amps is nowhere near enough to power a combat robot. maybe a tiny hobbyist sized robot experimenting platform, but not a serious fighting machine with drill drives that can suck over 100amps in combination. The transistor (instead of Mosfet) H-Bridge is far too lossy..

No Failsafe - essential for a combat bot

No mixing - Tank steering is possible or you could do it in your radio if its a flash one, but its much easier to do at the controller level.

Requires you to build a Pic Programmer - a much more complicated circuit than the 3-wire picaxe style interface, and you need a basic understanding of compilers, hex files and so on to use it.

Seperate Servo-PWM convertors and H-Bridges with multiple connection points just give you more places to get something wrong or something to fail in combat.

If you're looking for the cheapest possible solution, you are probably best off buying some Electronize's in from the UK. If you're looking to learn how to do it yourself, be prepared for it to cost you about 3x as much and take 10x as long as just buying them would, but you'll learn a lot along the way.. Wink
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Post Mon Mar 07, 2005 12:45 am 
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Glen
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hey brett, how much do you charge for the picaxe pre programmed and have you got any PCBs for that controller made yet?
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Post Sat Apr 02, 2005 9:22 pm 
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dyrodium
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Joined: 24 Aug 2004
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Hey! Can anyone can use the team mothbots relay control that's in vincent with smaller relays for an antweight speed control with a 3rd weapon channel (bigger relay)? Could anyone estimate the cost of it? If no one's going to make them, could someone tell me what parts i need and the estimated cost? Thanks Smile
I would imagine it would be the same but with less hardcore parts! Smile
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Post Thu Apr 07, 2005 10:45 pm 
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Knightrous
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I've got designs for a small on/off switching controller for ant/beetleweights using a 18X chip, but I've no time to actually build one as of yet. It would be fairly limited to around 1-2amp per drive channel and weapon switching would be one way 5-10amp (depends on the fet used).

Size/price, currently unknown.
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Post Fri Apr 08, 2005 6:28 pm 
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Philip
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You could buy a two way Electronize RC relay switch for about AU$45.
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Post Sat Apr 09, 2005 5:39 am 
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