My task: use rechargeable Li-Ion (or any others) batteries to power the PCS500
I have some questions. I ask you to help in their understanding.
What is my problem:
1 problem:
Rechargeable batteries gives different voltages at the beginning and the end of its discharge cycle
2 problem:
I know, that exist linear regulator L78xx in PCS500 and so I do not want to add to them external additional linear regulator (eg L7809)
3 problem:
Information from your sources - are very different - and i can not make a decision about the safety of the accumulator battery voltage range for PCS500.
Me arranges variant: 3 x Li-Ion Cell = from 8.6 …(11.7)… to 12.6 Volts
but,
in this supply voltage range have a questions for you:
1)
There will not be any damage to electronic circuit switching \ PCS500 off on VD3 (4.7v) + IC30 + [IC45-> IC22] + [T17 + T18 + T16] and whether it will work in normal mode for it?
There will not be any damage to “Calibration PCS500” when going beyond a recommended 9V … 10V supply range PCS500?
12.6 Volts is OK for the PCS500.
If beyond 9V, there may be problems in the operation.[quote]There will not be any damage to “Calibration PCS500” when going beyond a recommended 9V … 10V supply range PCS500?[/quote]Calibration and operation may fail if beyond 9V.
I’d suggest to put a DC/DC converter and some heavy filter capacitors between the input of the scope and the battery.
That way you have a stable (and possibly adjustable) power supply voltage.
Thank Velleman
This information is entirely consistent with my understanding of the circuit supply rails PCS500 based linear regulators L78xx.
And I hope that 12.6 …13V will not damage circuit components “on\off PCS500” based VD3 (4.7v) + IC30 + [IC45-> IC22] + [T17 + T18 + T16]
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Important (but not essential) correction:
I incorrectly gave 3xLi-Ion range as = from 8.6 … (11.7) … to 12.6 Volts = is false
faithful to be considered range = from 9.6 … (11.1) … to 12.6 Volts = is true
therefore :
the question of a breach of “Calibration PCS500” = not actual for 3xLi-Ion
There are important arguments against it:
fact:
a) PCS500 = ~ 800mA - my measurement (PCS500 is enabled but not active)
b) the minimum voltage to calibrate the PCS500 = 9V (look posts Velleman)
arguments against external L78xx
Main:
Linear Regulators (any) under the load of 50-70% of their nominal should - have L78xx stock + 2V (preferably + 3V) at its input. And if the delta (difference) of the input voltage and the output will be less L78xx +2 … 3V, it will be an decrease output voltage L78xx (in place 9V of those will be for example 8.9V). Thus battery should have a lower limit = 9V + 2V = 11V (in the state is low = discharged)
but Li-Ion (3x3.7V) at 11V = only 50-75% discharged. So need to use Li-Ion 4x3.7V - at a price that is more expensive and takes up more space.
Can remedy the situation by applying NiMh \ NiCd, but they are heavier in weight, volume on the same “VA” = x 1.5-2 greater, and most importantly, there is no flat “sheet” batteries.
Optional-1:
Linear Regulators - Switching Regulators, and (as you rightly said) need to have the smoothing capacitor. Note: I probyval connection without capacitor - and did not see the essential difference.
Optional-2:
Linear Regulators - for 0.8…1.0A - it’s desirable the cooling radiator - this I checked, as strongly heated even at 11 … 12V-> to-> 9V
And info_A:
PCS500 in the scheme have L7805 controller that must work perfectly at input 9V and moreover should work and input 7B, but - given the fact that there PCS500 = -5V power bus (for bipolar power IC) —> the unipolar voltage power to all devices is desirable x1,75…2.0 more, and we get = 9 … 10V DC for PCS500
And info_B:
PCS500 in the scheme have circuit “on\off PSC500” based VD3 (4.7v) + IC30 + [IC45-> IC22] + [T17 + T18 + T16], - which is powered directly from the DC input
That’s for the safety of the components of this particular circuit by reason of increasing the input voltage to 12.6V - I was worried.
Velleman disproved my fears on this problem - Thank Velleman (see the answers Velleman)
I have not tracked the maximum.
but I measured and idle mode, and signal processing 1 oscilloscope channel - and I did not see the essential difference: the current consumption is in the range of 700-900 milliamps. At the same time I understand - most of them consume the internal linear transducers L78xx.
the scheme is to CD with oscilloscope - a document: PCS500-9a_cir.pdf
I do not know whether I have the right to upload it to the public space
and I did not understand how to attach images to the post
but it does not matter.
document somewhere in the archive have been on this forum
I was afraid of the circuit diagram in of “enable\disable PCS500” - it could be damaged at a higher voltage. Especially because when I bought a new PCS500 from the store - he had a problem in the block “enable\disable PCS500” (it was fixed under warranty).
Especially there is a bottleneck Zender diode = 4.7v, on which can be allocated excess capacity at 12.6V DCin.
Circuit diagram is also built around the optocoupler IC30 divider + resistors circuit \ comparing the voltage at which the PCS500 receives a signal from the computer - and controls"enable\disable PCS500".
Same (rarely = 1 case of the 50) the device itself is not adequately respond to signals from the computer (PCS500 - is not turned off automatically when you exit the oscilloscope software).
Thus:
components of “enable\disable PCS500” are designed and operate at its limit parameters even with 9 … 10V
yes it is a good choice.
Thank you - it helped me to find another option = solutions use only one battery Li-Ion 3.7V (instead of three = 3x3.7V).
But …
there is an argument against the use of such DC \ DC converters:
They have a very high background noise on the power line (higher than the step-down DC). This can negatively affect the noise oscilloscope. Moreover - in this converters - there is strong high-frequency electro-magnetic radiation, and their need to place them in the shield frame.
note:
PCS500 - very well executed design PSB, but even so - it catches noise from cellular transmitter (even in the mode when the channel is closed to the oscilloscope to GND) I tried to solve the problem of high-frequency interference - but without a results.
(This problem I have with this interference - is extremely serious background = overstated by + 10-20dBm, but it is a theme of separate topic)