Woodstock Low Power

[Maximilian Hohmann]

Hello!

(02-14-2018 05:00 PM)BobVA Wrote:  As for the physical condition, I just moved my LP board to my nicest looking HP-25.

Same with me. I borrowed a very nice HP-25 keyboard for my Panamatik Low Power calculator. But I didn't touch it's perfectly working circuit board and used a non-working one specifically acquired from eBay for that purpose instead.
And I already wrote on this thread (or on a similar one) that I could not sacrifice a perfectly working Woodstock-series calculator to turn in into a low-power version. There still must be plenty of dead units out there which are much better suited for that task! It is just a matter of patience...

Regards
Max

NB: I soldered that 100µF capacitor into my board. No difference, unfortunately. Whenever the GPS is turned on and my LP25 goes into sleep mode (either by pressing "f divide" or using the power switch) it will wake up calling itself an "HP-00" and only disconnecting and reconnecting the batteries will bring it back to useful life. The simple workaround is to make sure that the GPS is turned off before the calculator gets turned off... I tried with fully charged NiMH batteries and with new Alkalines. No difference.

[Harald]

Has anyone tried switching the speed in GPS mode from knots to km/h? It doesn't seem to work for me. I get a "-" in front of the speed, but comparing it to my speedo in the car it still shows about half of that reading.

[Maximilian Hohmann]

(03-05-2018 09:46 AM)Harald Wrote:  Has anyone tried switching the speed in GPS mode from knots to km/h? It doesn't seem to work for me. I get a "-" in front of the speed, but comparing it to my speedo in the car it still shows about half of that reading.

That was one of the first things that I tried (with the same result). But I don't want to be a major PIA so I kept it for me. It's enough that my HP-25 LP keeps draining it's batteries from time to time with no apparent reason.

[PANAMATIK]

(03-05-2018 10:50 AM)Maximilian Hohmann Wrote:  

(03-05-2018 09:46 AM)Harald Wrote:  Has anyone tried switching the speed in GPS mode from knots to km/h? It doesn't seem to work for me. I get a "-" in front of the speed, but comparing it to my speedo in the car it still shows about half of that reading.

That was one of the first things that I tried (with the same result). But I don't want to be a major PIA so I kept it for me. It's enough that my HP-25 LP keeps draining it's batteries from time to time with no apparent reason.

I don't have a HP-25 LP GPS version at the moment here. But I will build one end of this week and will check the speed km/h knots problem.

Can you measure the current drain in sleep mode? It should be around 100 uA. I have feedback from other LP owners, which report, that the battery is working now for weeks. But leaving the ACT chip drains 4 mA current. It has to be removed or its power lines cut. This was not mentioned in the manual, because I didn't know it.

Bernhard

[Maximilian Hohmann]

Hello Bernhard,

(03-05-2018 01:12 PM)PANAMATIK Wrote:  Can you measure the current drain in sleep mode? It should be around 100 uA. I have feedback from other LP owners, which report, that the battery is working now for weeks. But leaving the ACT chip drains 4 mA current. It has to be removed or its power lines cut. This was not mentioned in the manual, because I didn't know it.

I will make the measurement one of these days. But I have a feeling that the current in sleep mode is not the problem. I have removed all components from the PCB some time ago. There are really only the traces left. Whenever I turn on the calculator I check the voltage display ("g divide") and it consistently shows something like 2,6V. For many days in a row. But sometimes I find it with the batteries totally discharged, way below 1V. Could that be the buck voltage converter that does not go into standby mode when it is supposed to? Maybe a pullup (or pulldown?) resistor on it's "enable" pin would solve the problem? But I don't know what this would do to your board.

Regards,
Max

NB: I must be the only living person who has yet to discover the secret function :-) (but then in my professional environment I have learnt not to play around with delicate electronics because that might end badly - like flying into a mountain or landing a mile short of the runway at night...)

[jjohnson873]

I have had my HP-25LP for about a month. I haven't had time to use it extensively, but I bring it out of sleep each day and make a few calculations. I have the GPS and IR-LED options. The GPS requires the boost regulator. I usually turn on the GPS to check accuracy of time and then used the EEX key to turn off the GPS. I always check the battery voltage. My NiMH batteries started out around 2.60 vdc and have remained between 2.53 - 2.59 vdc after one week of very light use. I always use the f-divide key to put it to sleep. If I get a chance, I'll try to make some current measurements when the calculator is in sleep mode, but it will likely be next week before I can get to it. I recall that the HP-25 LP takes <<5mA when running and the LED display is on.
~ Jim J.~

[PANAMATIK]

(03-05-2018 09:46 AM)Harald Wrote:  Has anyone tried switching the speed in GPS mode from knots to km/h? It doesn't seem to work for me. I get a "-" in front of the speed, but comparing it to my speedo in the car it still shows about half of that reading.

1.) I confirm this bug reported by Harald: Speed display in GPS mode always showed knots instead of km/h regardless of which was selected.

2.) Another bug reported: Steady display flag 15 didn't work for HP-34C, it didn't show the X register during PAUSE, only the blinking dot while program running was visible. Normal mode works. HP-25/29/67 were OK.

3.) [added] All 20 predefined mathematical constants are missing in version 1.03. Previous versions were OK.

I have fixed these for the next LP version 1.04, but it is not yet released. I'm also working on the update utility.

Any more bugs?

Bernhard

[jjohnson873]

(03-05-2018 09:46 AM)Harald Wrote:  Has anyone tried switching the speed in GPS mode from knots to km/h? It doesn't seem to work for me. I get a "-" in front of the speed, but comparing it to my speedo in the car it still shows about half of that reading.

Bernhard....can you also dedicate a GPS mode key for miles/hour for those of us still on the old Imperial unit system?

[Maximilian Hohmann]

Hello!

I now (think I) found out what causes the occasional total battery drain of my Panamatik LP calculator. As I suspected it is the voltage booster that feeds the GPS which causes it. When the battery voltage drops below a certain level the device turns itself on, probably because the high signal which inhbits the device is no longer recognised as high (my guess only of course). It will then stay on permanently and feed the GPS it's 3,3V until down to well below 1V, thereby completely discharging the batteries very quickly.

I have no idea how to solve this problem other than using a voltage converter which needs a high signal for turning it on (rather than off). Thereby falling battery voltage could never turn the device on. Another solution might be to put a diode between the battery and the positive input of the voltage booster thereby making sure that the high signal coming from the Panamatik board is always (0,2...0,6V, depending on the diode used) higher than the supply voltage. Howerver with decreasing battery voltage there will always come a time when the Panamatik board will quit working and the inhibit signal drops to zero.

[PANAMATIK]

Hello Max

According to the datasheet of the GPS voltage booster only input voltages above 1.2V would enable the booster. Even when battery voltage is as low as 2.0 volts, the /SHDN output should deliver >1.2V. I still cannot see why you have this problem. Perhaps the booster is defective, or the /SHDN wire has bad contact. I would offer to examine your calculator and test with low voltages if you sent it to me.

Bernhard

Excerpt from datasheet:

Quote:The SHDN can be driven low (typically under 0.4 V) to power down the regulator and turn off power to the load (unlike most boost regulators, the input power does not pass through to the output when the board is disabled). This pin is internally pulled up to VIN through an 100 kΩ resistor, so it can be left disconnected or connected directly to VIN if you do not need to use the disable feature. The disable threshold is a function of the input voltage as follows:

For VIN < 0.8 V, SHDN voltage must be below 0.1×VIN to disable the regulator and above 0.9×VIN to enable it.
For 0.8 V ≤ VIN ≤ 1.5 V, SHDN voltage must be below 0.2×VIN to disable the regulator and above 0.8×VIN to enable it.
For VIN > 1.5 V, SHDN voltage must be below 0.4 V to disable the regulator and above 1.2 V to enable it.

The input voltage, VIN, must be at least 0.5 V for the regulator to turn on. However, once the regulator is on, the input voltage can drop as low as 0.3 V and the 3.3 V output voltage will be maintained on VOUT.

[Maximilian Hohmann]

Hello Bernhard,

(03-25-2018 12:55 PM)PANAMATIK Wrote:  According to the datasheet of the GPS voltage booster only input voltages above 1.2V would enable the booster. ...

I had a thorough look at the datasheet in the meantime. There is a 100k pullup-resistor on the Polulu board that connects the SHDN (shutdown) pin with Vcc whenever there is no connection to that pin, thereby switching on the voltage booster by default. I now desoldered that resistor and leave it to the pulldown resistor in your Woodstock LP board to make sure that the voltage booster is disabled unless turned on explicitily. Over the next days/weeks I will observe the battery voltage and report what happens.

Regards
Max

[PANAMATIK]

(03-28-2018 05:15 PM)Maximilian Hohmann Wrote:  ...I now desoldered that resistor and leave it to the pulldown resistor in your Woodstock LP board ...

Hello Max

The /SHDN line does not have a pull down resistor on the LP board. It is connected directly to a PIC processor pin, which is low level when GPS is OFF. Thus removing the pull up resistor on the converter is a good idea anyway, because it reduces the sleep current by 30uA. I don't know whether this solves your problem, but give it a try.

Bernhard

[PANAMATIK]

The first Woodstock Low Power circuits were sold more than 20 times in january and february this year. The response was overwhelming. Thank you very much. All of the circuits are working. Now I have ordered a second batch from the manufacturer and received the board a few days ago. I have to prepare the circuits and to complete the bottom side assembly, which should not be too much work.



The software did not change very much since. Only a few minor bugs were found belonging to some of the less common calculator types like HP-33E or HP-38E, which I could fix.

My own HP-29 LP is running since january while only charging the batteries two times.

I hope everybody has found the hidden feature meanwhile. I think it is time to reveal it now. The sequence is f f - Have Fun!

Bernhard

[Harald]

(05-09-2018 12:30 PM)PANAMATIK Wrote:  The first Woodstock Low Power circuits were sold more than 20 times in january and february this year. The response was overwhelming. Thank you very much. All of the circuits are working. Now I have ordered a second batch from the manufacturer and received the board a few days ago. I have to prepare the circuits and to complete the bottom side assembly, which should not be too much work.



The software did not change very much since. Only a few minor bugs were found belonging to some of the less common calculator types like HP-33E or HP-38E, which I could fix.

My own HP-29 LP is running since january while only charging the batteries two times.

I hope everybody has found the hidden feature meanwhile. I think it is time to reveal it now. The sequence is f f - Have Fun!

Bernhard

Thanks for the reminder, I need to use my Woodstock LP more! Too many other toys to play with.
I keep forgetting all those brilliant features you built into it. I really need to use it more often!