RX Question

**simon** · 7th May 2004, 20:20

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

7th May 2004, 20:34

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** · 7th May 2004, 21:57

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** · 8th May 2004, 09:39

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** · 8th May 2004, 20:34

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** · 8th May 2004, 20:36

Oh sorry - Didnt see your post there Ian.

Dave moulds
Team Turbine

**talulah** · 25th May 2004, 15:40

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** · 25th May 2004, 19:38

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** · 26th May 2004, 13:24

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!