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Author Topic: USB power for dummies  (Read 1459 times)

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Offline jagraham

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USB power for dummies
« on: April 20, 2015, 11:41:02 AM »
New to USB power here. I've been just simply going through AAs for my recorders and have decided (with recent purchase of a DR-70d) that I need to have a better solution.

I have a basic USB charger for my phone and other gear like that. The name is Fremo Q-02 3200mAh, it has 5V/1A output. I've seen a charger with the same output recommended for the digital recorder, but it is 18000mAh. What I'm wondering is how the mAh value affects the recorder. Could I use my current charger, or would it be insufficient for the DR-70d? I'm a little pickier about this with a recorder vs. a phone, if you know what I mean.
Mics: Nak CM-300s, Nak CM-100s, CP-1s, CP-2s, AT-853s(Cards, Hypers, Omnis) CA-14s(Cards, Omnis)
Pres: CA STC-9200, CA-UBB
Recorders: Tascam DR-70D, DR-2D, Edirol R-09

ISO: 1 Teac ME-120, CP-3 Caps, AT-853 Subcard Caps

stevetoney

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Re: USB power for dummies
« Reply #1 on: April 20, 2015, 12:18:50 PM »
The mah number simply specifies the size of the battery you're connected to...the larger the mah the longer the battery will power your gear. 

The operable units that you're concerned with are the voltage and amperage ratings that need to be supplied to the USB connector on your 70D...5V and 1amp.

As an independent check of the above, the back of the DR70D manual calls out a separate wall wart...the model number is PS-P515U. 

http://www.amazon.com/PS-P515U-Adapter-Portable-Digital-Recorders/dp/B0053O6NMW/ref=sr_1_1?ie=UTF8&qid=1429546153&sr=8-1&keywords=tascam+ps-p515u+ac+adapter

The photo in the link shows that this is a 5V, 1.5A power supply.  5V  -  Check!  1.5amps is more than 1.0 Amps  - Check! 

So, the bottom line here is that the device you plug into the mini-USB port on the 70D needs to give you 5V and at least 1amp for the 70d to work right.  This is true whether you power it from a battery or from a USB device that plugs into a wall socket.  So if you buy an external battery, make sure that it is a 5V battery and that it supplies at least 1 amp.  Most of the batteries being discussed in the remote power section meet or exceed the amp rating, but some don't.
« Last Edit: April 20, 2015, 12:30:32 PM by tonedeaf »

Offline jagraham

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Re: USB power for dummies
« Reply #2 on: April 21, 2015, 09:19:28 AM »
Thanks Steve! That was helpful, sometimes I need things explained in lamen's terms. I appreciate the link, it's informative, but I don't think I'll be running this on AC power.

So I take it 7W isn't going to somehow overload the recorder? Or 1.5 or 2A? My primary concern is powering the 70d for as long as possible, but I also don't want to break the recorder with an insufficient battery.

And it seems like I could successfully run the 70d with my 3200mAh battery. But, it probably wouldn't last too long, especially if running 4ch. I'll buy one of these ~18000 mah batteries in the ~25 USD range.
Mics: Nak CM-300s, Nak CM-100s, CP-1s, CP-2s, AT-853s(Cards, Hypers, Omnis) CA-14s(Cards, Omnis)
Pres: CA STC-9200, CA-UBB
Recorders: Tascam DR-70D, DR-2D, Edirol R-09

ISO: 1 Teac ME-120, CP-3 Caps, AT-853 Subcard Caps

stevetoney

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Re: USB power for dummies
« Reply #3 on: April 21, 2015, 10:57:06 AM »
Thanks Steve! That was helpful, sometimes I need things explained in lamen's terms. I appreciate the link, it's informative, but I don't think I'll be running this on AC power.

You're welcome, glad to help.

So I take it 7W isn't going to somehow overload the recorder? Or 1.5 or 2A? My primary concern is powering the 70d for as long as possible, but I also don't want to break the recorder with an insufficient battery.

That's right...the amp rating on the supply side needs to exceed the amps needed by the device...and the DR70D should have fuses and such in the design to protect in case of shorts/exteme overcurrent situations. 

I'm a mechanical engineer so it helps me to think of electricity like water flowing through a garden hose...volts is like the pressure in the hose, current is the flowrate through the hose, and resistance is the number of twists/turns/kinks in the hose (as well as how rough the hose is on the inside surface).

So, if your DR70D needs 1 amp and your 'pump' supplies you with more flow/current than that, you're good. 

An analogy is your house which probably has 200amp supply.  Each circuit comes off either 15 or 30 amp breaker.  If only one circuit is energized in the house because only one appliance is on, you don't destroy the appliance even though the house has 200 amps at the circuit breaker.  The circuit breaker is like a fuse in your recorder to protect in the case of shorts/overcurrent, so the breakers are set to trip at 15 or 30amps of total current flow...or before the short causes the wires in the house heat up and start a fire!!!  (The analogy would be trying to force a zillion gallons of water through a 1/2 inch garden hose in a ridiculously short amount of time...in this case friction would cause the hose to heat up and fail.)

The other thing you don't want to do is put a 'pump' on your hose that outputs alot of pressure (volts) into your garden hose because then it will exceed the strength of the hose and the hose will split/crack (note that this is a different failure than heating up).  So, match your voltage output to what your device needs and you're fine. 

And it seems like I could successfully run the 70d with my 3200mAh battery. But, it probably wouldn't last too long, especially if running 4ch. I'll buy one of these ~18000 mah batteries in the ~25 USD range.

The manual says the DR70D pulls 5W peak.  Since it operates at 5V, that's 1amp or 1000ma.  Assuming the 3200mah rating on your battery is at 5V, that means you should get 3.2 hours of run time from that battery and 18 hours from the 18000mah battery.  I think you can probably assume slightly longer times since 5W is the stated as the max.
« Last Edit: April 21, 2015, 11:04:42 AM by tonedeaf »

Offline jagraham

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Re: USB power for dummies
« Reply #4 on: April 22, 2015, 10:09:04 AM »
Tried out the Fremo 3200 mAh with the 70D last night. I amazingly got somewhere around 6 hours of 4ch recording, no phantom from the 70d. Charged my phone after and the battery still had some juice, not sure how much. Hoping to replicate that tonight in the field. I'll be buying a better battery soon but this might just work in a pinch. I'll of course pack AAs just in case.

I've always been OK with just buying AAs for the 2 AA units, but I can't keep doing that with the 70D.
Mics: Nak CM-300s, Nak CM-100s, CP-1s, CP-2s, AT-853s(Cards, Hypers, Omnis) CA-14s(Cards, Omnis)
Pres: CA STC-9200, CA-UBB
Recorders: Tascam DR-70D, DR-2D, Edirol R-09

ISO: 1 Teac ME-120, CP-3 Caps, AT-853 Subcard Caps

 

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