Re: Servo rotation and 315Mhz T/R help

by jc27 on Wed Feb 19, 2014 1:46 am

Keyboard is back to normal. That was weird, never saw anything like that before. I am going to try another idea to supply the receiver with a separate power source. It isn't something that would be a part of the finished circuit, just something to try to get the transmitter/receiver combo to make the servo rotate. If it works, then I know that the USB power supply isn't strong enough to power the receiver and the servo.
Any ideas of how I can power this setup with the smallest number of batteries? I found a lithium 9v that has 1400mAh (i have a DC/DC converter with a 5v 1.5a output). Would it be enough to run everything and how long do you think it would last? I know I could go with a rechargeable lithium pack, but I'm not too keen on having something that could blow up right next to my head.
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by adafruit_support_bill on Wed Feb 19, 2014 7:22 am

Code: Select all
Would it be enough to run everything and how long do you think it would last?

To determine that, you need to know how much current the system will draw. Based on the fact that it overloaded your USB port, I would guess that it exceeded 500mA. You should measure to be sure:
http://learn.adafruit.com/multimeters/current
User avatar
adafruit_support_bill
 
Posts: 25556
Joined: Sat Feb 07, 2009 9:11 am

Re: Servo rotation and 315Mhz T/R help

by jc27 on Thu Feb 20, 2014 9:32 pm

1200-1400mAh should be enough to power everything. The circuit is not going to be used all the time, just sporadically so I would think the high current lithium 9v should last at least a little while.
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by adafruit_support_bill on Fri Feb 21, 2014 6:04 am

At 500mA, 1200-1400mAh would probably give you 2-3 hours. If only operated sporadically, you can expect much longer.
User avatar
adafruit_support_bill
 
Posts: 25556
Joined: Sat Feb 07, 2009 9:11 am

Re: Servo rotation and 315Mhz T/R help

by jc27 on Fri Feb 21, 2014 11:22 am

I'm thinking the current will be ok, now I just have to see what the minimum operating voltages are for the receiver, trinket and the servo. If i could get away with 4.8v then 4 AA batteries would work. I did see that radioshack has a 6AA battery holder which would provide over 5v but then I have to use a voltage regulator (i have one), but I have to see what the dropout voltage is on it.
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by jc27 on Fri Feb 21, 2014 11:29 am

This is what I was planning on using for the voltage regulation:
https://www.adafruit.com/products/1065# ... al_Details
This won't work will it?
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by adafruit_support_rick on Fri Feb 21, 2014 11:33 am

The Traco unit will work on 6.5V - 32V. 6 AA rechargeables will give you 7.2V, so that's OK.
User avatar
adafruit_support_rick
 
Posts: 8585
Joined: Tue Mar 15, 2011 10:42 am
Location: Buffalo, NY

Re: Servo rotation and 315Mhz T/R help

by jc27 on Fri Feb 21, 2014 11:41 am

Seems like I should just have you design and built it since most of the parts are going to be from you guys lol. I'm going to pick up the 4 and 6 AA battery holders from radioshack this weekend as well as try to power the receiver from a different source to see if it works. I think the code is where it needs to be, but if you have any other suggestions on it please let me know.
I have another thread concerning the trinket and playing a short sound clip and flashing an LED in time with the sound. If you can, could you take a look at it and let me know what you think? Is it even possible?
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by jc27 on Fri Feb 21, 2014 11:42 am

Since the Traco unit has a max of 1A, I wonder if it is going to be enough.
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by adafruit_support_rick on Fri Feb 21, 2014 11:53 am

Ah - I got the impression that you were going to be drawing on the order of 500mA.
User avatar
adafruit_support_rick
 
Posts: 8585
Joined: Tue Mar 15, 2011 10:42 am
Location: Buffalo, NY

Re: Servo rotation and 315Mhz T/R help

by jc27 on Fri Feb 21, 2014 12:01 pm

The servo draws around 500ma when it rotates, and I'm not sure what the receiver draws. I will figure that out this weekend. How much does the trinket draw since that is what I'm planning on using for the servo rotation control.
How much will the code need to be modified for it to work on a trinket?
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by jc27 on Mon Feb 24, 2014 9:25 pm

I'm starting to draw out my circuit schematic and I have a couple questions regarding power. If I use 4AA alkaline batteries, that would give me 6v, but how much current would I get from them? I was thinking of going with 4AA rechargeable batteries, but the output voltage would only be 4.8v, and the 5V trinket says that it should get around 5.5v or more to operate. I thought about using the 3.3v trinket, but I think that I read it won't work because of the 5v signal coming from the receiver going to the trinket input pin, is that correct?
Here are the power requirements for the components so far:
Servo 4.8-6vDC
Trinket 5.5-16vDC (or 3.5-16vDC for the 3.3 trinket)
315MHz receiver 4-15vDC
I was planning on using the traco 5v buck converter, but since it has a max of 1A, I am not sure it will be enough. I found the UBEC converter on the store and it outputs 5vDC at 3A, which would be more than enough. If I were to have an input of 7.2vDC (from 6AA rechargeables), would the 5vDC out be enough to power the 5v trinket (it recommends 5.5vDC)? Can the shrink wrap on the UBEC be removed and have header pins installed to be mounted to a PC board?
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by adafruit_support_rick on Tue Feb 25, 2014 10:10 am

Alkaline AA's will deliver around 700mA before they start to get hot.

The receiver is going to be low-power, and the arduino itself doesn't take much. I think the Traco has more than enough capacity for your application.

You can use a voltage divider on the output of the transmitter to get the signal down into range for the 3.3V trinket, but you'll still need 5V for the other components.

The 5.5V requirement for the trinket is when you go through the voltage regulator. I believe that you can attach a regulated 5V supply to the USB 5V pad.
jc27 wrote:Here are the power requirements for the components so far:
Servo 4.8-6vDC
Trinket 5.5-16vDC (or 3.5-16vDC for the 3.3 trinket)
315MHz receiver 4-15vDC


Given that, you don't need to use a voltage regulator at all. Each of your three components already has a voltage regulator, and all three will run from 6V.
User avatar
adafruit_support_rick
 
Posts: 8585
Joined: Tue Mar 15, 2011 10:42 am
Location: Buffalo, NY

Re: Servo rotation and 315Mhz T/R help

by jc27 on Tue Feb 25, 2014 10:32 am

I don't think the 700mA will be enough. The servo will draw around 500mA when it rotates, so the batteries will die pretty fast. What is the current draw of the trinket? If I go with 6AA rechargeables, that will give me 7.2v and the traco will step that down to 5v but it can only handle 1A.
This circuit will be used only occasionally, so maybe alkaline batteries will work. I need to build the whole thing on a breadboard to see how it works.
Once I do that I need to figure out how to move the code over to a trinket. Right now I'm using an Uno to get the code to work. Now that it seems like it will, I need to alter it to get it to work on a trinket. How would I do that? I know I need a different servo library, but is that it?
jc27
 
Posts: 38
Joined: Sun Nov 24, 2013 4:05 am

Re: Servo rotation and 315Mhz T/R help

by adafruit_support_rick on Tue Feb 25, 2014 11:15 am

The Trinket and the receiver will not draw 200mA together, so you should still be OK with alkalines.

You'll need to use the Adafruit_SoftServo library on the trinket.
User avatar
adafruit_support_rick
 
Posts: 8585
Joined: Tue Mar 15, 2011 10:42 am
Location: Buffalo, NY