I have finished the Nano+DRV8825 minimal with temp sensor version. It is working but the 5346b zener diode is getting very very hot. The 10a10 diode at the start of the circuit or the 5408 diodes that I use to smooth microsteps are also getting hot but not like this. I cannot touch it. The 2w 15ohm resistor is also getting hot but I can still touch it.
when I measure the voltage from the vin pin to ground I read 9.67v instead of 9.1v, so that might be the reason. The resistor is 15ohm I have checked it so there is nothing wrong there.
Actually, everything is working fine other than the faulty toggle switch which I'm going to replace, but I'm afraid to use it like this. I don't want anything to burn, I have spent quite some time making it. Hence my question; is this normal and should I not worry? if not what could be wrong? I have spare 5346b diodes that I can try but I have purchased all of them from the same seller on aliexpress.So they might be the same.
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Should not be hot at all. Looks like the board has a short or problem. Would measure voltage source, should be around 12V. So if 12V source, 1.2V drop across 10a10 diode, so other side of diode should measure 10.8V going into 15 ohm resistor. Then on other side of 15 ohm should be 9.1V across zener and going into VIN. Are you sure you also did not wire the 12V to the stepper motor from the wrong side of the 15 ohm resistor?
Turn everything off. Disconnect stepper motor.
Turn on external 12V, Measure current being drawn from 12V supply, should only be a few hundred milliamp or less going into board. If more this is issue and need to find where the current is going.
Arduino Power Consumption
Nano 20mA 20
5V LEDS for IN/OUT 20mA each 40
Buzzer 20mA 20
LCD1602I2C 20mA 20
PB switches 1mA 01
Zener Diode
The maximum current drawn by the Nano and other components is around 100mA. Could try using 24 – 26Ω 5W. There is around a total of 220mA (above when all components on plus the 120mA for the 15Ω resistor) flowing in the circuit (through the Zener) and 9.1V across the Zener, so the Watts equates to V x I or 9.1 x 0.192 or 1.76 Watts (the Zener is rated at 5W). In terms of powering the Nano, 192mA should be sufficient as we are only powering 2 in/out LED’s , switches, LCD, Nano and drv8825 input pins (and occasionally the buzzer)
On this basis the Zener should be relatively cool.
so current draw is 190mA for arduino+leds etc, thus total current draw through Zener = 192mA (2.9V across 15Ω) + 100mA, Thus Zener = voltage drop * current = 9.1 *300mA = 2.73 Watts = relatively cool to touch
If diodes 5xxx for microstepping are gettin hot, this is different issue. This is setting of pot voltage on drv882 or similar chip not set correctly. Chip is supplying too much voltage to stepper.
You should aim for 70% nominal current in single phase of stepper.
All power off.
Connect multimeter in series with one phase of stepper. Set to measure current. Then power on, set controller to FULL steps only with COIL POWER ON. Now set current using VREF pot on driver chip to 70% of full current (for recommended stepper this is 70% of 400mA which is 280mA. Now all set and diodes should be ok.
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The supply voltage is 12.2V and after the 10a10 diode it is 11.5V. I cannot measure dc current unfortunately(only ac) but yeah something is off with the arduino board(or the circuit) because it is also getting quite warm and shutting itself off after a while as I have observed today. I have checked for shorts and from 5v pin to ground pin for a second there is no resistance like measuring capacitors but I haven't put any(maybe there are on the board). changing the arduino is changing the whole thing basically so I will look for other solutions first. Other than that there are no shorts that I could find.
I will look for a voltmeter which can read dc current but meanwhile I can try a stone 26Ω 5W resistor, maybe it will balance things or add a diode in parallel. I don't think LM7809 would solve anything if there is a short in the circuit, instead of the diode the regulator will get too hot. Am I right? But I will try that also.
I have lowered the vref on the drv8825 from 0.5V to 0.4V diodes are still hot though. The stepper is rated 1A so I don't want to lower it too much and lose torque or miss microsteps. They aren't hot like the zener diode anyway.
Last edit: doramason 2016-09-14
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I have lowered the vref on the drv8825 from 0.5V to 0.4V diodes are still hot though
This still too high. Should be 0.35V for your stepper (Current Limit = VRef * 2) thus 0.35x2 = 700mA.
A lot of clone DRV8825 from ebay/china have wrong current sense resistor value on the DRV8825 so this is not an accurate way to set coil current. Best way is to measure the current in one coil of the stepper, with coil power On and set to full steps. Then adjust pot so current reads 700mA (for your stepper).
Because of the higher current your stepper needs then yes those diodes are going to get warm even after proper adjustment of pot.
Last edit: brownrb 2016-09-14
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Running a DRV8825 with 1A stepper is problematic. When both coils are energized this would mean the DRV8825 is running close to the limit at 2A flowing so no wonder the diodes are getting warm.
From the datasheet - The DRV8825 can supply up to 2.5-A peak or 1.75-A RMS output current.
With your stepper set to 70% of 1A = 0.7A, when both coils are energized when moving maximum would be 1.4A which is still a little on the high side as the DRV8825 is operating near its RMS value. With the recommended 400ma stepper that would be 280ma in each coil = 0.56A which is good as circuit and DRV8825 is operating well inside any limit. And the lower currents means less heat in the stepper and diodes.
It might be worth cutting a track on the board where the 12V rail goes to the DRV8825 pin VMOT. This would isolate that side of the equation. (and could easily resolder later).
The output of the 15 Ohm goes to only two components, the Zener and VIN. If you have verified this, then the next thing would be to isolate the VIN pin of the Nano. This effectively means only the Zener is connected to the output, so if it still gets hot then something is really amiss in the wiring. If you then measure more than 9.1V across the zener then thats an issue also. If its cold then something re the nano is a problem.
In some previous cases with the same problem users have found that the junction of zener/15R it was connected to +5 instead of VIN, that VMOT was actually connected to VIN, that the 15R resistor was wrong value, that the zener was connected the wrong way round. Some users have also found an issue with the Nano itself in that the voltage regulator on the nano itself that is connected to VIN on board sometimes goes faulty and causes this to happen.
So if when the nano VIN is disconnected and the resistor/zener is not hot, and you measure 9.1V, then when you reconnect VIN and resistor/zener gets hot, it points to faulty Nano.
If disconnect VIN and resistor/Nano still hot then there is issue with wiring on the board.
If you have a spare nano or uno lying around, breadboard just the Nano with a 15R and 9.1V zener as per circuit with junction of 15R/Zener going to VIN. Use a 12V external source (+12V to 15R input and 12Vgnd to Gnd on the nano - I often do this to test nanos I work with and normal good ones will always be ok. Bad ones (I have had a few) will cause zener/resistor to be hot.
Hope this helps
Robert
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I haven't done any of the mistakes you have stated and the resistor is 15.9 ohm if I'm remembering it correctly. Besides, I don't read 9.1V from vin pin to ground it is around 9.65V, so if it is an issue I'm having it already.
How am I going to isolate vin? Should I connect zener and the resistor to ground after disconnecting them from the vin pin?
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Hi
I have been doing some circuit analysis on this and bench testing with various loads and with different R values and Zener values.
Because the load of the Arduino varies depending upon what it is doing, from pretty much nothing to at least 100mA, this causes a variation in the voltage going to VIN. And can result in the resistor and zener getting hot.
To stablize the voltage to VIN, its probably best to use a voltage regulator such as LM7808. Using a TO-220 package means being able to use a heatsink to dissipate any heat. There is no way the Nano will draw anything close to the current limit of the LM7808 so thats a better choice.
I will modify all the circuits and docs and layouts (stripboard and PCB) and parts lists etc so that going forward, the LM7808 is the preferred choice. The circuit is earlier in this post. Changes will take some time to do, but no changes necessary in firmware or applications or drivers.
Cheers
Robert
Last edit: brownrb 2016-09-30
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One thing I have to correct; nano was not shutting itself down due to heat. it was disconnecting/reseting because I was rapidly moving the stepper in different positions to see if it was missing steps. I have solved it by increasing the baud rate, now it is not disconnecting or reseting. Actually with a heatsink on the zener I might use it like this till it's burned completely.
I have used a strip board. I'm not that handy with electronics that's why this took so much of my time and I don't want to change the nano because everthing is soldered to its legs. I can and will disconnect the zener and the resistor and try to see if they are getting hot on their own.
One thing I have noticed the 12v led is on when I connect the nano to usb. but shouldn't it be turned off till I connect the 12v supply? I mean from where is it getting the power? Is nano giving power to vin when it is connected to usb?
By the way can I omit the on/off switch? If I do omit what is the order of connecting cables? I'm guessing first stepper, sensor then the 12V supply and finally the usb. is this order correct? Also can I leave the firmware switch on all the time? is there a disadvantage of doing this?
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Disconnecting the zener/resistor from Vin - does not matter. My maths was all wrong due to not working out the impedance of the Arduino in the equation. Hence the 9.1V to VIN actually fluctuates all over the place. The LM7808 replacement will fix that.
Yes the 12V LED appears dim when 12V is not connected. Yes leakage related to VIN being the problem. Nothing one can do except place another diode into the circuit to stop that.
Yes to omitting ON/OFF.
If you do not have a permanent setup and are connecting/disconnecting cables etc then
1. Ensure no power anywhere
2. Always connect stepper first
3. Next connect temp probe
3. Next connect USB or 12V - does not matter in what order.
4. When USB connects, there is a reset of the arduino (depends on firmware switch)
The firmware switch - unless you are programming new firmware, leave it on. I only switch mine off when programming new firmware, then set it back on once its finished uploading.
I have ON/OFF just in case something goes wrong I can turn off power to stepper motor (as motor is drivern by 12V) quickly. If I;m at the scope. Never had to use it. I added it because the commercial one I purchased for around 400USD had a habit of winding out to infinity and ended up damaging my focuser - it never had an ON/OFF switch and I only found out when there was a grinding sound coming from the observatory which started a mad panic with cables being pulled out all over the place - thats why I added it to this design ..... The commercial one now sits in a box gathering dust...
Cheers
Robert
Last edit: brownrb 2016-09-30
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Conversly, when finshed for the night
1. Ensure all power is OFF (12V) then remove 12V cable
2. remove usb cable next
3. then disconnect stepper and temp probe
4. pack it all away
Last edit: brownrb 2016-09-16
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thanks for all the info, I will order LM7809 regulator. But are you sure with that diagram? The one on the data sheet states higher values for capacitors. I'm attaching it. I will be waiting for your answer to order the correct ones.
I have an unrelated question about the software; is it possible to increase maxsteps beyond 65000? I have changed it in the arduino code but still the application limits it. I'm using a baader steeltrack focuser with belt and a pulley on the fine focus knob so with 1/32 microstepping I need a much higher limit. I know that the resolution will be ridiculous and I don't actually need it, even halfstep is more than enough for me. But at 1/32 microstep stepper runs much more silent with less vibration and because I have added the diodes it runs very smoothly hence I wanna use it like that.
Also do you know any ascom compatible software that does autofocus with canon dslr? Backyardeos can't even move the focuser properly.
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The circuit will be using an LM7808 regulator with 0.33uF and 0.1uF ceramic capacitors.
Ok, re position - there are a number of factors in play - email me direct. Tell me your focuser .ino file
At present the arduino file actually uses type long so yes, it can support higher values than 65000.
However, will need some changes in Windows App and ASCOM driver. Let me write some code so that I can send you a new Windows App and ASCOM driver to test that would support a greater value.
Autofocus with Canon EOS - try APT.
Another user has mentioned this an we could be working on a direct control of the EOS lens using the Arduino focuser controller...... (no promises)
Cheers
Robert
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I just made some quick changes to the winapp and arduino code. Will 12 million steps be enough? (actually I have yet to test the limit which will be more). Let me know
Cheers
Robert
I will make the 7808 circuit with the stated capacitors. Thanks for telling me about APT, I will definetely try it.
I didn't understand what did you mean by focuser .ino file. At 1/32 microsteps, 65000 steps move the focuser 6.6mm(though the focuser isn't casted/machined perfectly so I read different measurements like 6.2mm from other locations with a caliper). I think that makes 0.1 micron per step. I have a newtonian so my focuser moves at most 30mm so I need 300000 steps if I haven't calculated incorrectly. 12 million is a bit too much :) but maybe someone with a refractor or rc might need that number.
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The focuser .ino is the file you use to program the nano with - something like Focuserv244_DRV8825_HW203_M.ino
With the new windows app and changes to your .ino file (like the one above) then it will easily set 300000 steps as the maximum (maxStep). I will need to send you instructions on how to do the config using the Windows app. Please email me direct at zzzzzzzzz and let me know the .ino file you are using with your nano.
Cheers
Robert
Last edit: brownrb 2016-09-19
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I have finished the Nano+DRV8825 minimal with temp sensor version. It is working but the 5346b zener diode is getting very very hot. The 10a10 diode at the start of the circuit or the 5408 diodes that I use to smooth microsteps are also getting hot but not like this. I cannot touch it. The 2w 15ohm resistor is also getting hot but I can still touch it.
when I measure the voltage from the vin pin to ground I read 9.67v instead of 9.1v, so that might be the reason. The resistor is 15ohm I have checked it so there is nothing wrong there.
Actually, everything is working fine other than the faulty toggle switch which I'm going to replace, but I'm afraid to use it like this. I don't want anything to burn, I have spent quite some time making it. Hence my question; is this normal and should I not worry? if not what could be wrong? I have spare 5346b diodes that I can try but I have purchased all of them from the same seller on aliexpress.So they might be the same.
What would you say about putting another diode in parallel? They might share the load wouldn't they? What could go wrong?
Should not be hot at all. Looks like the board has a short or problem. Would measure voltage source, should be around 12V. So if 12V source, 1.2V drop across 10a10 diode, so other side of diode should measure 10.8V going into 15 ohm resistor. Then on other side of 15 ohm should be 9.1V across zener and going into VIN. Are you sure you also did not wire the 12V to the stepper motor from the wrong side of the 15 ohm resistor?
Turn everything off. Disconnect stepper motor.
Turn on external 12V, Measure current being drawn from 12V supply, should only be a few hundred milliamp or less going into board. If more this is issue and need to find where the current is going.
Arduino Power Consumption
Nano 20mA 20
5V LEDS for IN/OUT 20mA each 40
Buzzer 20mA 20
LCD1602I2C 20mA 20
PB switches 1mA 01
Zener Diode
The maximum current drawn by the Nano and other components is around 100mA. Could try using 24 – 26Ω 5W. There is around a total of 220mA (above when all components on plus the 120mA for the 15Ω resistor) flowing in the circuit (through the Zener) and 9.1V across the Zener, so the Watts equates to V x I or 9.1 x 0.192 or 1.76 Watts (the Zener is rated at 5W). In terms of powering the Nano, 192mA should be sufficient as we are only powering 2 in/out LED’s , switches, LCD, Nano and drv8825 input pins (and occasionally the buzzer)
On this basis the Zener should be relatively cool.
so current draw is 190mA for arduino+leds etc, thus total current draw through Zener = 192mA (2.9V across 15Ω) + 100mA, Thus Zener = voltage drop * current = 9.1 *300mA = 2.73 Watts = relatively cool to touch
http://www.reuk.co.uk/wordpress/electric-circuit/zener-diode-voltage-regulator/
If problem persists, you could try using LM7809 voltage regulator. I attach diagram here from circuitstoday.com
If diodes 5xxx for microstepping are gettin hot, this is different issue. This is setting of pot voltage on drv882 or similar chip not set correctly. Chip is supplying too much voltage to stepper.
You should aim for 70% nominal current in single phase of stepper.
All power off.
Connect multimeter in series with one phase of stepper. Set to measure current. Then power on, set controller to FULL steps only with COIL POWER ON. Now set current using VREF pot on driver chip to 70% of full current (for recommended stepper this is 70% of 400mA which is 280mA. Now all set and diodes should be ok.
The supply voltage is 12.2V and after the 10a10 diode it is 11.5V. I cannot measure dc current unfortunately(only ac) but yeah something is off with the arduino board(or the circuit) because it is also getting quite warm and shutting itself off after a while as I have observed today. I have checked for shorts and from 5v pin to ground pin for a second there is no resistance like measuring capacitors but I haven't put any(maybe there are on the board). changing the arduino is changing the whole thing basically so I will look for other solutions first. Other than that there are no shorts that I could find.
I will look for a voltmeter which can read dc current but meanwhile I can try a stone 26Ω 5W resistor, maybe it will balance things or add a diode in parallel. I don't think LM7809 would solve anything if there is a short in the circuit, instead of the diode the regulator will get too hot. Am I right? But I will try that also.
I have lowered the vref on the drv8825 from 0.5V to 0.4V diodes are still hot though. The stepper is rated 1A so I don't want to lower it too much and lose torque or miss microsteps. They aren't hot like the zener diode anyway.
Last edit: doramason 2016-09-14
I have lowered the vref on the drv8825 from 0.5V to 0.4V diodes are still hot though
This still too high. Should be 0.35V for your stepper (Current Limit = VRef * 2) thus 0.35x2 = 700mA.
A lot of clone DRV8825 from ebay/china have wrong current sense resistor value on the DRV8825 so this is not an accurate way to set coil current. Best way is to measure the current in one coil of the stepper, with coil power On and set to full steps. Then adjust pot so current reads 700mA (for your stepper).
Because of the higher current your stepper needs then yes those diodes are going to get warm even after proper adjustment of pot.
Last edit: brownrb 2016-09-14
Running a DRV8825 with 1A stepper is problematic. When both coils are energized this would mean the DRV8825 is running close to the limit at 2A flowing so no wonder the diodes are getting warm.
From the datasheet - The DRV8825 can supply up to 2.5-A peak or 1.75-A RMS output current.
With your stepper set to 70% of 1A = 0.7A, when both coils are energized when moving maximum would be 1.4A which is still a little on the high side as the DRV8825 is operating near its RMS value. With the recommended 400ma stepper that would be 280ma in each coil = 0.56A which is good as circuit and DRV8825 is operating well inside any limit. And the lower currents means less heat in the stepper and diodes.
It might be worth cutting a track on the board where the 12V rail goes to the DRV8825 pin VMOT. This would isolate that side of the equation. (and could easily resolder later).
The output of the 15 Ohm goes to only two components, the Zener and VIN. If you have verified this, then the next thing would be to isolate the VIN pin of the Nano. This effectively means only the Zener is connected to the output, so if it still gets hot then something is really amiss in the wiring. If you then measure more than 9.1V across the zener then thats an issue also. If its cold then something re the nano is a problem.
In some previous cases with the same problem users have found that the junction of zener/15R it was connected to +5 instead of VIN, that VMOT was actually connected to VIN, that the 15R resistor was wrong value, that the zener was connected the wrong way round. Some users have also found an issue with the Nano itself in that the voltage regulator on the nano itself that is connected to VIN on board sometimes goes faulty and causes this to happen.
So if when the nano VIN is disconnected and the resistor/zener is not hot, and you measure 9.1V, then when you reconnect VIN and resistor/zener gets hot, it points to faulty Nano.
If disconnect VIN and resistor/Nano still hot then there is issue with wiring on the board.
If you have a spare nano or uno lying around, breadboard just the Nano with a 15R and 9.1V zener as per circuit with junction of 15R/Zener going to VIN. Use a 12V external source (+12V to 15R input and 12Vgnd to Gnd on the nano - I often do this to test nanos I work with and normal good ones will always be ok. Bad ones (I have had a few) will cause zener/resistor to be hot.
Hope this helps
Robert
thanks for the detailed answer. yes it is nano v3. actually this is the one I have bought; https://www.aliexpress.com/item/Nano-V3-ATmega328-CH340G-Micro-USB-Pin-headers-NOT-soldered-Compatible-for-Arduino-Nano-V3-0/32664577152.html?spm=2114.13010608.0.101.tEsb0p
I haven't done any of the mistakes you have stated and the resistor is 15.9 ohm if I'm remembering it correctly. Besides, I don't read 9.1V from vin pin to ground it is around 9.65V, so if it is an issue I'm having it already.
How am I going to isolate vin? Should I connect zener and the resistor to ground after disconnecting them from the vin pin?
this for stripboard
If you used the 15p headers to connect the nano you could simply remove the nano?
Last edit: brownrb 2016-09-16
Hi
I have been doing some circuit analysis on this and bench testing with various loads and with different R values and Zener values.
Because the load of the Arduino varies depending upon what it is doing, from pretty much nothing to at least 100mA, this causes a variation in the voltage going to VIN. And can result in the resistor and zener getting hot.
To stablize the voltage to VIN, its probably best to use a voltage regulator such as LM7808. Using a TO-220 package means being able to use a heatsink to dissipate any heat. There is no way the Nano will draw anything close to the current limit of the LM7808 so thats a better choice.
I will modify all the circuits and docs and layouts (stripboard and PCB) and parts lists etc so that going forward, the LM7808 is the preferred choice. The circuit is earlier in this post. Changes will take some time to do, but no changes necessary in firmware or applications or drivers.
Cheers
Robert
Last edit: brownrb 2016-09-30
One thing I have to correct; nano was not shutting itself down due to heat. it was disconnecting/reseting because I was rapidly moving the stepper in different positions to see if it was missing steps. I have solved it by increasing the baud rate, now it is not disconnecting or reseting. Actually with a heatsink on the zener I might use it like this till it's burned completely.
I have used a strip board. I'm not that handy with electronics that's why this took so much of my time and I don't want to change the nano because everthing is soldered to its legs. I can and will disconnect the zener and the resistor and try to see if they are getting hot on their own.
One thing I have noticed the 12v led is on when I connect the nano to usb. but shouldn't it be turned off till I connect the 12v supply? I mean from where is it getting the power? Is nano giving power to vin when it is connected to usb?
By the way can I omit the on/off switch? If I do omit what is the order of connecting cables? I'm guessing first stepper, sensor then the 12V supply and finally the usb. is this order correct? Also can I leave the firmware switch on all the time? is there a disadvantage of doing this?
Disconnecting the zener/resistor from Vin - does not matter. My maths was all wrong due to not working out the impedance of the Arduino in the equation. Hence the 9.1V to VIN actually fluctuates all over the place. The LM7808 replacement will fix that.
Yes the 12V LED appears dim when 12V is not connected. Yes leakage related to VIN being the problem. Nothing one can do except place another diode into the circuit to stop that.
Yes to omitting ON/OFF.
If you do not have a permanent setup and are connecting/disconnecting cables etc then
1. Ensure no power anywhere
2. Always connect stepper first
3. Next connect temp probe
3. Next connect USB or 12V - does not matter in what order.
4. When USB connects, there is a reset of the arduino (depends on firmware switch)
The firmware switch - unless you are programming new firmware, leave it on. I only switch mine off when programming new firmware, then set it back on once its finished uploading.
I have ON/OFF just in case something goes wrong I can turn off power to stepper motor (as motor is drivern by 12V) quickly. If I;m at the scope. Never had to use it. I added it because the commercial one I purchased for around 400USD had a habit of winding out to infinity and ended up damaging my focuser - it never had an ON/OFF switch and I only found out when there was a grinding sound coming from the observatory which started a mad panic with cables being pulled out all over the place - thats why I added it to this design ..... The commercial one now sits in a box gathering dust...
Cheers
Robert
Last edit: brownrb 2016-09-30
Conversly, when finshed for the night
1. Ensure all power is OFF (12V) then remove 12V cable
2. remove usb cable next
3. then disconnect stepper and temp probe
4. pack it all away
Last edit: brownrb 2016-09-16
thanks for all the info, I will order LM7809 regulator. But are you sure with that diagram? The one on the data sheet states higher values for capacitors. I'm attaching it. I will be waiting for your answer to order the correct ones.
I have an unrelated question about the software; is it possible to increase maxsteps beyond 65000? I have changed it in the arduino code but still the application limits it. I'm using a baader steeltrack focuser with belt and a pulley on the fine focus knob so with 1/32 microstepping I need a much higher limit. I know that the resolution will be ridiculous and I don't actually need it, even halfstep is more than enough for me. But at 1/32 microstep stepper runs much more silent with less vibration and because I have added the diodes it runs very smoothly hence I wanna use it like that.
Also do you know any ascom compatible software that does autofocus with canon dslr? Backyardeos can't even move the focuser properly.
The circuit will be using an LM7808 regulator with 0.33uF and 0.1uF ceramic capacitors.
Ok, re position - there are a number of factors in play - email me direct. Tell me your focuser .ino file
At present the arduino file actually uses type long so yes, it can support higher values than 65000.
However, will need some changes in Windows App and ASCOM driver. Let me write some code so that I can send you a new Windows App and ASCOM driver to test that would support a greater value.
Autofocus with Canon EOS - try APT.
Another user has mentioned this an we could be working on a direct control of the EOS lens using the Arduino focuser controller...... (no promises)
Cheers
Robert
I just made some quick changes to the winapp and arduino code. Will 12 million steps be enough? (actually I have yet to test the limit which will be more). Let me know
Cheers
Robert
Here is the correct LM7808 8V circuit.
I will make the 7808 circuit with the stated capacitors. Thanks for telling me about APT, I will definetely try it.
I didn't understand what did you mean by focuser .ino file. At 1/32 microsteps, 65000 steps move the focuser 6.6mm(though the focuser isn't casted/machined perfectly so I read different measurements like 6.2mm from other locations with a caliper). I think that makes 0.1 micron per step. I have a newtonian so my focuser moves at most 30mm so I need 300000 steps if I haven't calculated incorrectly. 12 million is a bit too much :) but maybe someone with a refractor or rc might need that number.
The focuser .ino is the file you use to program the nano with - something like Focuserv244_DRV8825_HW203_M.ino
With the new windows app and changes to your .ino file (like the one above) then it will easily set 300000 steps as the maximum (maxStep). I will need to send you instructions on how to do the config using the Windows app. Please email me direct at zzzzzzzzz and let me know the .ino file you are using with your nano.
Cheers
Robert
Last edit: brownrb 2016-09-19