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Electronics => Electronics => Topic started by: Sylvestre on July 31, 2011, 11:27:11 PM

Title: Noob Question about voltage requirements
Post by: Sylvestre on July 31, 2011, 11:27:11 PM
Hey guys,

This may sound like a real novice question.  If the axon II's maximum voltage is ten volts how would you power something that requires more voltage such as a 24 volt motor or 5 LEDS that require 3.3 volts each?  Sorry to waster your guys' time, but I never learned this and I'm new to robotics. If someone could help me that'd be great.

Thanks
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on July 31, 2011, 11:29:33 PM
Also what would I have to do to run two 24 volt batteries with the axon II
Title: Re: Noob Question about voltage requirements
Post by: DangerousElectrician on August 01, 2011, 10:07:28 AM
Put another voltage regulator in front of the axon to regulate the voltage from 24V to 10V, then feed the 10V into the axon. If you are very skilled with a soldering iron, you could replace the voltage regulators on the axon with ones that can handle higher input voltages.

To control a 24 volt motor you'll need relays or transistors (read this http://www.kpsec.freeuk.com/trancirc.htm (http://www.kpsec.freeuk.com/trancirc.htm)). If you lack the electrical knowledge to build a motor driver, consider buying a motor driver (here's one http://www.sparkfun.com/products/9668 (http://www.sparkfun.com/products/9668)).

Controlling the LEDs will require a transistor or relay. The LEDs can be powered off the 24V directly but will require a current limiting resistor (read this http://www.kpsec.freeuk.com/components/led.htm (http://www.kpsec.freeuk.com/components/led.htm))
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 01, 2011, 10:51:59 AM
Ok so by putting a voltage regulator on my circuit am I just losing power?  Would I be better off getting two smaller batteries?  Would the motors still get full power from the batteries with voltage regulator or do I lose some of the power from the voltage regulator?  Last question, is it possible that motor driver for that motor driver to control two 12 volt motors?
Title: Re: Noob Question about voltage requirements
Post by: corrado33 on August 02, 2011, 02:58:48 PM
Ok so by putting a voltage regulator on my circuit am I just losing power?

A normal voltage regulator converts energy into heat, so yes, you're losing power.  (I may or may not have said that right.)  A switching regulator is much more efficient. 
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 02, 2011, 04:28:16 PM
What is a battery you guys would recommend for the axon mote?  Hawker?
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 03, 2011, 09:19:32 PM
Hi,

What is a VERY POWERFUL battery you guys would recommend for the axon mote?  Hawker?
Asking such just reveals that you care more for the *My balls are bigger than yours* kinda thing, rather than careful selecting the battery that is the best fit for what you need.
A too large battery mans you're dragging dead weight and as such, that you are not running it optimally.

Further, we don't use subjective terms in engineering, since we all have different ideas of what eg. "VERY POWERFUL" means.
Consider instead your actual needs (load and runtime) and select a battery to cover that with some margin.
Forget the power drawn by the controller board - the major part of the load are taken by the motor(s) and other actuators you might use.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 03, 2011, 10:32:16 PM
No actually I was just looking for a battery people may have used in the past that they found successful.  Not the saying you said above.  Excuse my misuse of words.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 03, 2011, 10:34:02 PM
Also the motors will require a separate power source
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 05, 2011, 08:20:54 AM
Hi,

No actually I was just looking for a battery people may have used in the past that they found successful.  Not the saying you said above.  Excuse my misuse of words.
OK then, what are your loads, besides the controller?
24V Motor current?
1 or 2 motors?
The 5 LEDs are they supposed to be on/off concurrently?
Do you have other loads to consider?  (If so, please list voltage/current for those).

And for how long do you want it to run between recharges?

If you answer all of the above, the best suited battery can be found.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 05, 2011, 09:11:04 AM

If so Im going to use two 24 volt 450 watt motors.  I want it to go 9 mph and I want it run 2 hours before I have to recharge.



I'm going to connect a gps, search light, rangefinder, 3 servos, and a infrared camera to the axon mote.  I'm not sure about the specs on these.  I'm just looking for the battery/batteries i need for the motors.

Title: Re: Noob Question about voltage requirements
Post by: waltr on August 05, 2011, 09:58:47 AM
Quick calculation:

450W / 24V = 18.75Amps per motor, 37.5Amps for both motors.
37.5Amps times 2 hours = 75 Amp-Hour battery capacity as the minimum requirement.

Look in the above "Robot Tutorials" for a more detailed explanation.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 05, 2011, 07:33:09 PM
I will be able to control those with this motor driver then, right?

http://dimensionengineering.com/Sabertooth2X25.htm (http://dimensionengineering.com/Sabertooth2X25.htm)

When it says 6-24 volt nominal I assume thats input from the battery, but will I lose power if my motors require 24 volt each?  That probably doesn't matter because it meets the amp requirements, right?
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 05, 2011, 09:16:11 PM
Hi,

I will be able to control those with this motor driver then, right?
[Snip link to Sabertooth 2X25.]
Yes, 450W at 24V is (450/24=) 18.75A and the driver can handle 25A - you'd need to use the current limiters though, as your motors will try to grab a good deal over 25A at startup and reversal.

When buying a battery, add around 20% to the capacity requirement, as the capacity decreases somewhat over time - a 90Ah battery would cover that.

And get a golf cart/Marine batteriy - they can handle deep discharge, which  a truck battery cannot.
(Prepare to pay through your nose though).


When it says 6-24 volt nominal I assume thats input from the battery, but will I lose power if my motors require 24 volt each?  That probably doesn't matter because it meets the amp requirements, right?
It will be fine. Not because of the current, but the small loss there'll be at any given current is a smaller percentage at a high voltage. Assume you loose half a volt at a given current. at 6V, that would be (0.5*100/6=) 8.3%, while st 24V it will just be (0.5*100/24=) 2.1%

With such hungry motors, the rest of the loads will be close to invisible in the greater picture, but the 450W will only be when given 100% PWM (which, strictly speaking isn't PWM at all). At any lower speeds, consumption will be less.

Use a switch mode converter to go from 24V to eg. 6.0V to 6.5V and regulate the rest of the way down to 5.0V with a LDO linear regulator, then your losses will be small, while still getting a very clean 5V line.
A linear regulation from 24V to 5V means an efficiency of 20%, while a switcher can give you from 80% to 95%, as the average current draw will be the load current divided by the conversion rate.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 05, 2011, 10:48:05 PM
What I had in mind is that I will be hooking up the motor driver to an axon II.  I'll have two separate batteries.  One for the Axon and one for the motors.  I'm not sure if I quite understood the last paragraph correctly.  I wouldn't need a switch mode converter or linear regulation if I was using a separate battery for the axon, would I?  Also it says in the description of the sabertooth that in can handle 50 amps for a few seconds (startup and reversal).  I'm using scooter motors.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 09, 2011, 05:13:56 PM
If someone could verify that I am doing everything correctly, I'd really appreciate it.
Title: Re: Noob Question about voltage requirements
Post by: corrado33 on August 09, 2011, 05:22:43 PM
To answer one of your questions, no, you would not need to do the switching regulator and LDO if you had two separate batteries.  With that said, I think two separate batteries complicates things.  

That's just my opinion.  You could very well use two batteries.  (But then you have to charge two batteries, check the voltage of two batteries..., buy two batteries...)

Basically what soeren was saying in his last paragraph is that you would use a switching regulator (which is good at dropping voltages way down without losing a lot of energy as heat), to regulate the 24V battery to about 6volts.  Then you would use a LDO (low drop out) linear regulator to regulate it to 5V because (I'm making assumptions here) it gives you a cleaner DC signal than the switching regulator would.  AND, it's easy for a linear regulator to regulate such a small voltage drop so not that much heat is lost, giving you good efficiency.  A low drop out linear regulator simply means that it can work with a very small input/output voltage difference.  So you can provide it with a lower voltage source than a normal linear regulator.

I can't help you with the sabertooth questions as I have no experience with it.  
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 09, 2011, 05:51:38 PM
Ok so I would be able to run both the axon and the motor driver at the same time.  I may need some help wiring this up.  Thanks a lot though  :)
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 09, 2011, 09:04:56 PM
Hi,

[...] I wouldn't need a switch mode converter or linear regulation if I was using a separate battery for the axon, would I?
With a separate battery you'd still need a voltage regulator, preferably an LDO regulator.
If you use eg. a 4 cell NiMH battery, they'll be at up to 5.8V when freshly charged and will discharge to somewhere between 3.6V and 4.4V (depending on discharge current).

So, the battery goes from too high a voltage, to a too low voltage (if you use any standard 5V components, which usually needs at least 4.5V, you cannot discharge it fully, i.e. a shorter runtime than the nominal capacity suggests).
A 6 cell battery is the best in that respect, going from ~8.7V down to 5.4V - 7.2V and an LDO will keep the logic happy, by providing a steady 5V throughout the discharge curve.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 10, 2011, 12:48:28 PM
Ok the recommended voltage for an axon is 6 volts. Which regulator do I buy? Would any of these from this website work? http://www.dimensionengineering.com/ (http://www.dimensionengineering.com/)
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 11, 2011, 12:44:40 AM
Hi,

Ok the recommended voltage for an axon is 6 volts. Which regulator do I buy?
None.
I didn't realize that it was for running an Axon, which has got an LDO installed. I am not aware of which make and model the LDO is, but typically, LDO's require less than 1V (some less than a tenth of that). Any 5V LDO can stand at least 10V input and most do better, so just connect a 6 cell battery to the input terminal of the Axon and you will be able to use most, if not all of its available charge (some is lost as heat in the LDO).

You can find the datasheet for the LDO if you google its name and it will tell you the drop out voltage as well as the maximum input voltage.


Would any of these from this website work? http://www.dimensionengineering.com/ (http://www.dimensionengineering.com/)
If you were to use a single 12V battery, their switchers would be a way to switch down to 6..7V for feeding the LDO (although it can be done much cheaper), but when using a separate battery, they're only needed if you want to make do with fewer battery cells (as it can switch up as well as down).
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 11, 2011, 09:14:01 PM
Ok I didn't quite understand that last paragraph.  ???  Can you possibly explain what the circuitry will look like just for the battery, motor driver, and axon.  Basically how I'm going to connect these parts.
Title: Re: Noob Question about voltage requirements
Post by: Gertlex on August 11, 2011, 09:38:14 PM
In the last paragraph, Soeren meant switching regulators ("switchers" apparently).  They're basically the same, functionally as regular voltage regulators, but they're much more efficient (aka less heat produced, less energy drained from the battery)

I've attached a picture :D  The wires from axon don't necessarily go to the right pins on the motor driver but whatever.  Having not used PWM with the axon, I don't know where the PWM signal comes from offhand, either... but hopefully it helps :)
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 12, 2011, 08:57:13 AM
Thanks for that schematic!  I'm not sure which switching regulator I should get though.  Any suggestions?  Could I use this adjustable regulator? http://www.dimensionengineering.com/DE-SWADJ3.htm (http://www.dimensionengineering.com/DE-SWADJ3.htm)
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 14, 2011, 04:09:05 PM
Hi,

Ok I didn't quite understand that last paragraph.  ???
You can go about it in a couple of ways:
1) Use only a 12V battery and then a switch mode regulator for getting the 5V
2) Use  two batteries12V and something lower. The lower voltage battery could bnefit from a buck/boost switchmode regulator, as it can generate a stable +5V from both lower and higher voltages, so the battery can be drained properly between recharges.
3) Check in the datasheet of the Axon voltage regulator if it is contend with up to 15V or higher - if so, you can run the Axon from the 12V battery, although you'd need a larger heatsink as the heat to dissipate is: (Ubatt-5V)/I [W]
Where Ubatt is simply the battery voltage, the 5V is what the regulator outputs and I is the current
drawn.


Can you possibly explain what the circuitry will look like just for the battery, motor driver, and axon.  Basically how I'm going to connect these parts.
Are you going for a single battery or the "one for the motors and one for the logic/sensors"?

Basically, the 5V side is easily fed from the 12V battery, in the same way that you would with 2 batteries - only here you derive the low voltage from the 12V rather than another battery.

If you don't need all that much current, this (http://www.romanblack.com/smps/a02.htm) is another (very cheap) option if you want to switch down and you can easily change the output voltage to eg. ~6V.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 14, 2011, 06:48:08 PM
Thanks for that.  I decided I'm going to use a separate battery for the motors and a separate battery for the electronics to avoid brownouts.  I'm going to need a lot of current from the battery because I will be powering wireless camera that gives me a live video feed.  That will powered by the battery that corresponds to the electronics.  Also I will be running many sensors/devices off of the axon II (ie gps, range finder, search lights, servo) so i will be needing a lot of current.
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 15, 2011, 06:47:44 AM
Hi,

I decided I'm going to use a separate battery for the motors and a separate battery for the electronics to avoid brownouts.
OK, then we only need to talk about the low voltage.


I'm going to need a lot of current from the battery because I will be powering wireless camera that gives me a live video feed.  That will powered by the battery that corresponds to the electronics.  Also I will be running many sensors/devices off of the axon II (ie gps, range finder, search lights, servo) so i will be needing a lot of current.
It's hard to say how much current you need without knowing exactly what you are going to load the battery with, but if it is over (or just near) the limit of the onboard voltage regulator, you'll need a separate regulator for some of the extra equipment.
Since it would be a little harder to change the regulator on the Axon, should it give up it's mojo, perhaps just load it at half what it can handle and draw the rest from an external regulator.

An external regulator for this is easy to make - the regulator IC, a few caps and perhaps a couple of resistors (if using a variable regulator). And as with all the rest... Fuses are paramount. Mount one for each tap from the batteries, as close to the battery terminal as possible.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 15, 2011, 12:13:56 PM
Once I figure out the which parts (gps, servo, etc) I am going to use, I'll post the specifications (current/voltage required) on here of each one and we'll figure it out from there.
Title: Re: Noob Question about voltage requirements
Post by: Gertlex on August 15, 2011, 04:57:22 PM
Once I figure out the which parts (gps, servo, etc) I am going to use, I'll post the specifications (current/voltage required) on here of each one and we'll figure it out from there.

Sounds good.  As a friendly tip, when you post that list, also post your guess as to how you'll split the power requirements.  That way we can spy any incorrect concepts you might have picked up (we all learn/infer incorrect ideas :) )
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 20, 2011, 01:07:17 PM
Ok here is the list:

(2) 24 volt motors-
22 amps each (separate battery, 55 ah)

(1) Xtend modem-
Supply voltage: 2.8 - 5.5VDC regulated
Frequency band: 902 - 928MHz
Serial data interface: 3V - 5V CMOS UART - No configuration required
Transmit current: 730 mA (@ 5V, 1W TX Power Output)
Receive current: 80 mA (@ 5V, 1W TX Power Output)


(1) Axon II
(http://www.societyofrobots.com/axon2/axon2_datasheet.shtml (http://www.societyofrobots.com/axon2/axon2_datasheet.shtml))

(2) LEDS
3.3 volts @ 25 ma each

(1) GPS
3.3V @ 41mA

(3) Hitec HS-645MG servos
-Operating Voltage- 4.8-6 volts
-Idle Current- 8.8 ma
-Running Current- 350 ma
-
(1) Sabertooth 2x25 motor driver  (WILL BE POWERED BY A SEPARATE BATTERY THAN THE ELECTRONICS TO AVOID BROWNOUTS)
Specs: 25A continuous, 50A peak per channel.
6-24V nominal, 30V absolute maximum

The following items will not be connected to the Axon II, but will run off the same battery.

(1) Cantek CTTN501R24 Outdoor IP67 Bullet Camera with 24 IR LEDs
-Requires 12 vdc, doesn't say current requirements (http://www.123securityproducts.com/tn501r24.html (http://www.123securityproducts.com/tn501r24.html))

(1) 2.4 Ghz transmitter and receiver set (Comes with a wall transformer to plug into your home outlet, but I will just cut the transformer from the wires and then hook the wires up to the battery). No specs.
http://www.123-cctv.com/seccams/trans.html (http://www.123-cctv.com/seccams/trans.html)

Also I want my robot to run for 1 hour- 1 hour & 1/2 so I was thinking I'd probably need a 55 ah battery for the motors.  I'm not sure how large the battery should be for the electronics.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 21, 2011, 03:59:35 PM
So what voltage regulators will I need, how many AH will the battery be for the electronics (everything besides motors), and what will the circuitry look like?  Specs are posted above of all the electrical components
Title: Re: Noob Question about voltage requirements
Post by: adanvasco on August 22, 2011, 11:38:15 AM
You might as well use two different power supplies by separating the circuits. Take a look at the $50 robot tutorial and you'll get an idea on how to do this.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 22, 2011, 03:01:40 PM
That's what I had in mind (I said this in an earlier post).  I'm going to have one battery for the motors and one battery for the electronics (everything except motors and motor driver).  Basically, I'm just looking for what my circuit will look like, what regulators I need, the battery I need for my electronics, and if there is any other things I need/ should know.
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 22, 2011, 03:16:08 PM
Hi,

So what voltage regulators will I need, how many AH will the battery be for the electronics (everything besides motors), and what will the circuitry look like?  Specs are posted above of all the electrical components
You seem to think that we're somehow obliged to do your footwork?

You add the max. current consumptions of each unit that you want to be supplied by the +5V line.
If that comes to eg. 2A, you need a 2Ah battery for 1 hour of runtime and 3Ah for 1.5 hour.
Actually, you need to get a somewhat higher capacity battery, as the capacity rating is for a 20 hour discharge and the capacity falls with rising current draw and the battery is gonna get worn over time as well, so go for 30% to 50% more capacity than your calculations indicate.

When you have calculated the total consumption on the +5V line, it's time to start adding a regulator.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 22, 2011, 04:44:25 PM
Ok thank you.  I'm sorry, but I am just looking for some help and a starting point.  That's all.  That's exactly what you gave me.  Thanks.

So I added up all of the current draws for the hardware that'll be on the electrical battery and I got about 3 amps or 3051 ma (I did not add up the current the Axon II draws).  So if I wanted it to run for 1.5 hours I assume I should use a 10-15 AH battery just to be safe (considering I didn't add the current required from the Axon II), or am I wrong?

I am still a bit confused on the regulators though?  How do I figure out which one I need?
Title: Re: Noob Question about voltage requirements
Post by: rbtying on August 22, 2011, 06:56:28 PM
If you need 3A at 5V, you get a regulator (preferably a switching one) which is rated for 5-6A or more at 5V. Usually a good choice for this amount of current is an R/C "BEC", which are commonly rated at ~5A/5V. Another option would be one of these (http://www.pololu.com/catalog/product/2111).

And no, not quite: 3A * 1.5 hrs = 4.5 Ah, then overspec the battery leads to 7-8Ah. Of course, a 10-15 Ah battery will work, it'll just be large/expensive/heavy.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 22, 2011, 08:33:52 PM
If I wanted the Axon II and the video transmitter and receiver to run on 12 volt  I won't need a regulator, right?  If I need to boost the voltage from 12 volt to 24 volt, will I need a voltage regulator work or does the the Sabertooth motor driver take care of that?
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 22, 2011, 10:42:10 PM
Just drew up this schematic.  I will definitely take criticism because I know I did something wrong  ;D.  I still have the same questions as I did in the post above.  Where it got cut off, it says 12 volt 12 AH battery.  I forgot a few things; a fuse in between battery and motor driver and an IC to measure how much battery I have left.  Also the wireless rf modem that connects to the UART and power of the Axon II
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 24, 2011, 09:22:08 PM
Also, there will be a 5 volt cooling fan
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 25, 2011, 01:21:25 PM
Hi,

Just drew up this schematic.  I will definitely take criticism because I know I did something wrong  ;D. 
And right you are...  :D


I still have the same questions as I did in the post above. 
Please post by using "modify" instead of chain posting, or answers will either not happen, be confusing or, as I have decided to do, just happen to a single of several chain posts.


Where it got cut off, it says 12 volt 12 AH battery. 
Using two batteries of 12V doesn't make sense. In that case it would be better to just use one.


I forgot a few things; a fuse in between battery and motor driver and an IC to measure how much battery I have left.
Instead, you added capacitors and they'll be fine as fuses, restricting any bit of current flow at all  ;)
Most of the writing on the "schematic" is intelligible and the bit in the middle, right of the controller is a bit of a mystery to me?

'And no, no motordriver will make the 12V into 24V and even if it did, that would mean a current draw from the battery of more than 88A!

You could draw such diagrams in Eagle with 100% clarity.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 25, 2011, 01:59:54 PM

Quote
Using two batteries of 12V doesn't make sense. In that case it would be better to just use one.

I would use two batteries to avoid brownouts. 

Quote
right of the controller is a bit of a mystery to me?

Basically, that's just the wireless camera setup (transmitter, receiver, camera).

Quote
And no, no motordriver will make the 12V into 24V and even if it did, that would mean a current draw from the battery of more than 88A!

Could I use a boost converter to boost the voltage?


Will I need any voltage regulation to output a steady voltage?

Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 25, 2011, 02:48:39 PM
Hi,

I would use two batteries to avoid brownouts. 
All your logic runs on a regulated 5V. This leaves a very wide margin for voltage drops of the battery before they would get through to the logic and if you fear that's gonna happen with a correct wired and sound battery, a power buffer for the logic is easy to implement.
Assuming the bare logic takes 100mA (it's probably less) and the brownout time is 10ms (it's probably shorter), then a diode and a 220µF capacitor will make sure the supply keeps the voltage OK.


Basically, that's just the wireless camera setup (transmitter, receiver, camera).
Aha. Why would you have a receiver on the 'bot?


Could I use a boost converter to boost the voltage?
Yes, if you're able to make a boost switcher for such high currents. You will find it hard to get an efficiency of more than 80%, Which means the peak current will be huge.

This sets quite hard demands for the battery and the input capacitors of the switcher and since the average drain will be around 110A (including losses), you'd need a battery of more than 200Ah for a 1.5 hour runtime.

It would be fair to tell you that a I know several experienced engineers that wouldn't touch such a project with a long stick.
Neither would I, as the sensible way to get the 24V in your app. is to connect two 12V batteries in series (same type, age and capacity).


Will I need any voltage regulation to output a steady voltage?
Yes.
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 25, 2011, 03:15:41 PM
Quote
All your logic runs on a regulated 5V. This leaves a very wide margin for voltage drops of the battery before they would get through to the logic and if you fear that's gonna happen with a correct wired and sound battery, a power buffer for the logic is easy to implement.
Assuming the bare logic takes 100mA (it's probably less) and the brownout time is 10ms (it's probably shorter), then a diode and a 220µF capacitor will make sure the supply keeps the voltage OK
Ok thank you for the advice on the capacitor.  I'll do that instead of using a separate battery to power the motors.

Quote
Aha. Why would you have a receiver on the 'bot?
Oh man I am getting my terms mixed up :P.  I meant to say just the transmitter and camera.

Quote
It would be fair to tell you that a I know several experienced engineers that wouldn't touch such a project with a long stick.
Neither would I, as the sensible way to get the 24V in your app. is to connect two 12V batteries in series (same type, age and capacity).

Yes that is a brilliant idea.  The solution you explained would be more than I could handle (money and knowledge).  I'll buy two 12 volt 75 AH batteries.


If I use capacitors to regulate the motors and the Axon II already has on board regulation will I still need regulators?
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 25, 2011, 03:41:27 PM
Hi,

If I use capacitors to regulate the motors and the Axon II already has on board regulation will I still need regulators?
Capacitors doesn't regulate and I'm not sure what you mean?

As I already mentioned, you have to find a datasheet for the regulator used on the Axon and see what input it can handle.
You shouldn't tap 12V from one of the series connected batteries, as that will unbalance their charge.

A simple buck switcher taking the 24V down to 6..8V would be the best way to feed from the two series connected batteries. You could use more than one switcher.

If you use something like this (http://www.romanblack.com/smps/a03.htm) and change ZD1 to somewhere around 7..8V, you'd get a reasonable input for 5V LDO's (with a peak efficiency of around 94% at 200mA and still in the high eighties at 7he max. of 700mA).
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 25, 2011, 04:13:39 PM
My motor driver will regulate the current and voltage applied to my motors. Could I use a product like this to regulate the voltage and current applied to the electronics (everything besides motors)?

http://www.google.com/products/catalog?hl=en&rlz=1C1RNCC_enUS321US321&q=dc+to+dc+converter+12+volt+5+amp&gs_upl=6799l10714l2l10790l6l5l0l0l0l0l214l615l0.3.1l4l0&bav=on.2,or.r_gc.r_pw.&biw=1280&bih=666&um=1&ie=UTF-8&tbm=shop&cid=3288733956479599320&sa=X&ei=APJWTsfFC8eKsQLPmdW3DA&ved=0CHkQ8wIwAg (http://www.google.com/products/catalog?hl=en&rlz=1C1RNCC_enUS321US321&q=dc+to+dc+converter+12+volt+5+amp&gs_upl=6799l10714l2l10790l6l5l0l0l0l0l214l615l0.3.1l4l0&bav=on.2,or.r_gc.r_pw.&biw=1280&bih=666&um=1&ie=UTF-8&tbm=shop&cid=3288733956479599320&sa=X&ei=APJWTsfFC8eKsQLPmdW3DA&ved=0CHkQ8wIwAg)
Title: Re: Noob Question about voltage requirements
Post by: Soeren on August 25, 2011, 09:24:07 PM
Hi,

My motor driver will regulate the current and voltage applied to my motors. Could I use a product like this to regulate the voltage and current applied to the electronics (everything besides motors)?

http://www.google.com/products/catalog?hl=en&rlz=1C1RNCC_enUS321US321&q=dc+to+dc+converter+12+volt+5+amp&gs_upl=6799l10714l2l10790l6l5l0l0l0l0l214l615l0.3.1l4l0&bav=on.2,or.r_gc.r_pw.&biw=1280&bih=666&um=1&ie=UTF-8&tbm=shop&cid=3288733956479599320&sa=X&ei=APJWTsfFC8eKsQLPmdW3DA&ved=0CHkQ8wIwAg (http://www.google.com/products/catalog?hl=en&rlz=1C1RNCC_enUS321US321&q=dc+to+dc+converter+12+volt+5+amp&gs_upl=6799l10714l2l10790l6l5l0l0l0l0l214l615l0.3.1l4l0&bav=on.2,or.r_gc.r_pw.&biw=1280&bih=666&um=1&ie=UTF-8&tbm=shop&cid=3288733956479599320&sa=X&ei=APJWTsfFC8eKsQLPmdW3DA&ved=0CHkQ8wIwAg)
What did the datasheet on the voltage regulator say?
And how high a voltage will the rest of the equipment handle?
Title: Re: Noob Question about voltage requirements
Post by: Sylvestre on August 25, 2011, 09:43:08 PM
Here are the main specs:

INPUT voltage 20 to 32 VDC
OUTPUT voltage 13.8 VDC
Efficiency >92 %
Output current: 5 amps
max output current: 5.5 amps

Datasheet URL:
http://www.samlexamerica.com/customer_support/pdf/SlickSheets/SDC-5_Samlex_Specifications.pdf (http://www.samlexamerica.com/customer_support/pdf/SlickSheets/SDC-5_Samlex_Specifications.pdf)

The axon II can handle 5-15 input voltage
The transmitter and camera just says it requires a 12 volt input voltage