Help Understanding Operating Specs of Step Up Regulator

Thread Starter

djsfantasi

Joined Apr 11, 2010
9,156
I have ordered a 9V Step-Up Voltage Regulator after destroying a similar variable output device (don't ask and I won't tell). My motivation was that all I needed was 9VDC from 5.2VDC and the variable feature was unnecessary (and made the replacement cost higher).

In reviewing the specs, I noticed a 1.4A input maximum. I always understood that a device only drew what it needed from a larger, maximum supply current. This is being powered from a PC power supply at 5VDC. The supply is rated at 8A. Is this going to cause a problem? (Note that I hadn't hooked the earlier regulator to this power supply...)

As a little background, I had something working for years, but when I added a new device (Arduino Mega, drawing an additional 40mA), my system stopped working. That is when the manufacturer of the non-functioning device (an SSC-32 from Robotshop) suggested taking my 5.2VDC input, boosting it to 9VDC, so the mis-performing circuit could successfully regulate it to 5VDC. I thought it was strange (Boost 5V to 9V to regulate it to 5V?!?), but decided to give it a go since the manufacturer said it did not support 5.2VDC input.

I also suspect that the Mega couldn't talk successfully to the device at 115,200bps (although that speed is supported), so in addition to re-powering my system, I've configured communications to take place at 9,600bps.
Capture.PNG
So do you think I am OK with my Boost Regulator? What do I have to look out for?
 

Hypatia's Protege

Joined Mar 1, 2015
3,228
In reviewing the specs, I noticed a 1.4A input maximum. I always understood that a device only drew what it needed from a larger, maximum supply current.
I believe the specification is reflexive of the output current (i.e. the load must draw no more current than that which occasions a regulator input current of 1.4A)...


the manufacturer of the non-functioning device (an SSC-32 from Robotshop) suggested taking my 5.2VDC input, boosting it to 9VDC, so the mis-performing circuit could successfully regulate it to 5VDC. I thought it was strange (Boost 5V to 9V to regulate it to 5V?!?), but decided to give it a go since the manufacturer said it did not support 5.2VDC input.
That's according to reason!:)
'Step down' VRs (whether 'switching' or linear) require input EMF greater than their designed (or 'programed') output --- Application of input EMFs less than the (desired) regulator output plus said 'dropout offset' will result in no, low and/or noisy output...

So do you think I am OK with my Boost Regulator? What do I have to look out for?
I think you're 'good to go' --- One caveat though - Please take care to assure that the (boost) regulator's output will never see less than its minimum load Spec! --- HV 'spikes', etc are phenomena that digital systems can live without!:eek:

I also suspect that the Mega couldn't talk successfully to the device at 115,200bps
The 'underpowered' condition of the VR was probably 'messing with' the RS232 levels as well - It is well worth your while to recheck it at full speed once the system is properly powered:D


Best regards
HP
 
Last edited:

Brownout

Joined Jan 10, 2012
2,390
In reviewing the specs, I noticed a 1.4A input maximum. I always understood that a device only drew what it needed from a larger, maximum supply current. This is being powered from a PC power supply at 5VDC. The supply is rated at 8A. Is this going to cause a problem? (Note that I hadn't hooked the earlier regulator to this power supply...)
You understood correctly. I think the spec should have said "minimum" input current for the supplied power. Your power supply is more than capable to supply this current.


So do you think I am OK with my Boost Regulator? What do I have to look out for?
I do.
 
Last edited:

Thread Starter

djsfantasi

Joined Apr 11, 2010
9,156
Thanks for the comment. The company has discounted the replacement and is sending it to me for the cost of shipping alone. Pololu has been great.
 
Top