RX Question

[simon]

Is there any circuit that I can buy that will allow me to power my receiver from my SLA batts ?

[team_ireland]

RX Question

Yes Its called a BEC Battery Eliminator Circuit

Basically it will take an input of a certin voltage and out put 5v constant. If you have a soldering iron and a farnell/maplin/rs/rapid electronics catelogue you should be able to build one very very cheeply.

http://www20.brinkster.com/antweights/5%20Volt%20Regulator.htmlhttp://www20.brinkster.com/antweight...Regulator.html

Here is a guide from my website. Its very simple and with 16v capacators will only work to about 12v but if you put in higher voltage caps you should be able to power it from 24v. However I do not advise this. I would advise using a 2 step regulator to first drop the voltage to 12v and then down to 5v. You can find the information for this here

http://www.teambigbro.co.uk/regulator.htmlhttp://www.teambigbro.co.uk/regulator.html

If you should prefer to buy one you can purchase a 4.5v regulator from technobots reletaviely cheeply (but not as cheep as you can make one):

http://www.technobots.co.uk/en-gb/dept_408.htmlhttp://www.technobots.co.uk/en-gb/dept_408.html

But if you want really no hastle and dont want to worry about anything else with it simply the best BEC out there is found here:

http://www.robotcombat.com/marketplace_elect_other.htmlhttp://www.robotcombat.com/marketplace_elect_other.html

This is expensive but is a mighty fine piece of kit.

Hope this helps you.
Regards
Ian

[craig_anto]

RX Question

i have got the robot combat BEC and after 3 weeks of waiting it arrived on a huge box with it just rattling around in a bit of newpaper, and to top it all it doesnt work

make your own simon might be best


craig

[simon]

RX Question

Thanks guys. Think I will purchase one. Me and delicate circuits dont really mix. Im more of a blow torch than a soldering iron type of guy

[Mouldy]

RX Question

Simon- Theres a diagram of how to make a simple 1 on the Bigger brother website...I can nearly understand it so it must be simple! and my team mate Ed wallace made one and it worked quite nicely...

Dave moulds
Team Turbine

[Mouldy]

RX Question

Oh sorry - Didnt see your post there Ian.

Dave moulds
Team Turbine

[talulah]

RX Question

I would advise against using a BEC. It may work for you, or you may end up with the most horrific EMC and radio comms problems imagineable.

I have conversed with many roboteers about this subject, and in conclusion, a rechargeable radio receiver battery is the best option, with a link that allows it to be recharged from the SLA.

If you have opto-isolated control lines between your receiver and speed controller, then using a BEC simply allows the noise to bypass the optos.

See my EMC page for more info about conducted interference. I think Ill add a section specifically on BECs and why theyre not a good idea.

Good luck anyway!

[jim]

RX Question

Hi Paul, Nice to see you back on the forum.

I have used a BEC succesfully in the past, with two linear voltage regulators and a ferrite-core inductor, but I now find I can run all the radio & logic circuits for several hours on a 9v PP3 battery . Its smaller than the BEC used to be.

[talulah]

RX Question

Hi Jim, from the east side of Didsbury to the west!

Yes, the thing about the interference problems that BECs can introduce is that they are very specific to the robot they are used on, the wiring, position of screening materials, antennas etc. Theyll work fine on some machines and not on others.

Thats why I say generally, from the design outset, dont use them. However, if youve finished your robot and it works fine with a BEC, then thats great - dont take it out!

Adding series inductive filtering to the regulator circuit like you did will help to keep sharp transients getting through the regulators, but it wont cure problems much if youre already having trouble. Its amusing that your PP3 battery ends up smaller than the BEC anyway!

[talulah]

RX Question

I said above that I would add a section to my website on BECs. Ive just looked and noticed that there is already a whole page about them there already!

Its here: http://homepages.which.net/~paul.hills/Emc/Bec.htmlhttp://homepages.which.net/~paul.hills/Emc/Bec.html

Just goes to show how large my site has grown that I cant remember whats in there!

[Guest]

RX Question

http://www.koolflightsystems.com/ultimatebec.htmhttp://www.koolflightsystems.com/ultimatebec.htm
this will handle up to 3amps continuous and on the better versions 6v

[talulah]

RX Question

Note that most commercial BECs are designed for RC planes that generally do not have 100 Amp electric motors. Our motors and cables tend to create a bit more radiated and conducted interference than RC planes motors!

[big_nipper]

RX Question

I was trying to uses a 30A RC plane speedo to power the compressor but it kept cutting out. Also tried it on 24V set to half speed for 12V compressors but the BEC shut down at 18V so I cut it off. Although it worked on its own it would not work with the drive connected and had terrible interferance. Could have been something to do with not having a voltreg on it and powering the 5V side from the Rx battery. The speedo was rated at 6-12 Cells but the only limiting factor is the BEC, beyond that it will work upto a max of 30V where it would try and clamp the supply.

I still want a 12V compressor to work off a 24V battery that can be controlled from the Rx & a pressure switch. So Im currently building something. Surly someone else outthere must have already done this. If so how did you do it?

[jdwacken]

RX Question

I was planning a 24v compressor driven system before I discovered that the motors/gear ratio made the robot uncontrollable so Ive since cut down to 12V.

However, when I was using 24V the method I was going to use to solve the fried compressor problem was to use two in series, hopefully giving a faster recharge time and definitely giving 12V per compressor.

Of course, this wont be an option if youve not got the space or weight which, having seen the interior of Big Nipper, seems likely.

[big_nipper]

RX Question

My brother was lightening it last night while I try and fixup the electrics. Therere may be space but we dont have the weight. He lost 1.5kg, only another 2kg left. Mind you when we started the base plate on its own was nearly 20kg! And it doesnt help when the valve is nearly as big as the ram.

Using the IBC controller I few things came up. First was we bolted the heatsink to the chasis. As it turns out the heat sink is connected to the battery +ve. Big flashes when a ground lead touched the chasis. Problem solved by using insulating kits for the MOSFET that didnt have them fitted. It also turned out that the weapon channels can only switch upto 12V as there is a voltage clamp on it and I wanted to connected it to the 24V solinod directly as it could supply enough current. Actually I connected it anyway as the instructions didnt give a max voltage limit and the valve kept clicking every time the battery was connected and I thought the IBC was not working. It turned out be clamping it to 12V so I had 12V across the coil when off and 24V when on. This was easily fixed by altering the clamp to the battery voltage.

Back on subject. A range check with the BEC built into the IBC controller gave no noticeable reduction in range from using a 4.8V Rx battery. Although the IBC doesnt have opto-isolators on the Rx wires. Range was alot further than big nipper. That is without the Compressor running.