Talk:DIYbio:Notebook/Open Gel Box 2.0/Power Supply: Difference between revisions
(Added figure 4, Nixie power supply schematic) |
(nixie projects) |
||
Line 1: | Line 1: | ||
== Gel Box Power Supply Discussion Page <html> <a href="http://openwetware.org/wiki/DIYbio:Notebook/Open_Gel_Box_2.0/RFC1">O_G_B_2.0 Specification</a></html>== | == Gel Box Power Supply Discussion Page <html> <a href="http://openwetware.org/wiki/DIYbio:Notebook/Open_Gel_Box_2.0/RFC1">O_G_B_2.0 Specification</a></html>== | ||
'''Jan 17, 2009''' *'''[[User:Jonathan Cline|jcline@ieee.org]] 02:46, 17 January 2009 (EST)''': | |||
If anyone wants to try building & using a '''nixie supply''', there are kits | |||
available with all parts included & pro-looking silk screened PCB's. | |||
This kit is $16 though only outputs 10mA so it may not work, though | |||
interesting experiment (180v): | |||
http://www.ledsales.com.au/cart.php?target=product&product_id=52&category_id=16 | |||
This surface mount supply is variable 150-220VDC @ 50 mA output. Input | |||
is 12VDC@1000mA from a GlobTek transformer adapter (aka: common wall | |||
wart)... which means a PC's ATX supply would also do for the +12V | |||
(overkill of course). | |||
Only $50 pre-assembled! | |||
http://www.ogilumen.com/nixie-tube-power-supply-p-91.html | |||
See the attached PDF. It looks like they use a custom inductor. | |||
and, | |||
http://www.electricstuff.co.uk/nixpsu.html | |||
It should be possible to modify the voltage range lower. However for higher | |||
current carefully check the PCB, since the traces may not support | |||
higher current (at the high voltage). These supplies are ipod-nano | |||
size, because the current is so low. | |||
'''Jan 13, 2009''' [[User:Philip McIntosh|Philip McIntosh]] | '''Jan 13, 2009''' [[User:Philip McIntosh|Philip McIntosh]] |
Revision as of 00:46, 17 January 2009
Gel Box Power Supply Discussion Page <html> <a href="http://openwetware.org/wiki/DIYbio:Notebook/Open_Gel_Box_2.0/RFC1">O_G_B_2.0 Specification</a></html>
Jan 17, 2009 *jcline@ieee.org 02:46, 17 January 2009 (EST): If anyone wants to try building & using a nixie supply, there are kits available with all parts included & pro-looking silk screened PCB's.
This kit is $16 though only outputs 10mA so it may not work, though interesting experiment (180v): http://www.ledsales.com.au/cart.php?target=product&product_id=52&category_id=16
This surface mount supply is variable 150-220VDC @ 50 mA output. Input is 12VDC@1000mA from a GlobTek transformer adapter (aka: common wall wart)... which means a PC's ATX supply would also do for the +12V (overkill of course). Only $50 pre-assembled! http://www.ogilumen.com/nixie-tube-power-supply-p-91.html See the attached PDF. It looks like they use a custom inductor.
and, http://www.electricstuff.co.uk/nixpsu.html
It should be possible to modify the voltage range lower. However for higher current carefully check the PCB, since the traces may not support higher current (at the high voltage). These supplies are ipod-nano size, because the current is so low.
Jan 13, 2009 Philip McIntosh
Here is the Nixie power supply schematic mentioned by J. Cline. Posted with permission from http://www.electricstuff.co.uk/nixpsu.html, courtesy of Mike Harrison.
Figure 4. Nixie power supply schematic
Jan 11, 2009 Jason Morrison
"Sodium boric acid: a Tris-free, cooler. conductive medium for DNA electrophoresis."
With a sodium boric acid buffer (which they strongly recommend - see paper), for a 10cm gel, they went from 75min @125V (their standard for TAE/TBE buffer) to 16min @ 350V, or 35V/cm.
Jan 10, 2009 (Phil McIntosh 0938)
Figure 3. 300 VDC variable power supply circuit
Jan 08, 2009
I put together a bridge rectifier + RC, drawing from a variac, today, seems to give pretty stable voltage in the 0-180VDC range. The variac should give 120Hz oscillations, and the RC should do some decent smoothing. If you do this, be careful! We blew a couple bridge rectifiers before putting a resistor before the capactior to slow its [dis]charge cycle. I'll put it on the oscilloscope in a day or two, and see how well this does.
The bridge rectifier was like $2.50 for 400V/8A rating at radio shack. Notes and pictures: http://jayunit.net/2009/01/08/kitmakers-class/
Jan 08, 2009 Added link to Gel Box 2.0 Draft specification at top of page.
Jan 08, 2009
Comments from Peter Wendt, provider of the power supply schematic in Figure 1 below:
The supply itself is fairly well known and there had been discussions on those already on various newsgroups for instance. It is simple, it is easy to build, it uses only "generic" parts and is relatively cheap - however limited.
The downsides are the transformers (weight, size and losses) and the fact that you should keep an eye on the total power drawn from the "intermediate stage" and the high voltage end as well until the feeding transformer gets overloaded. Results might be better if the driving transformer is significantly bigger than the driven transformer - which adds more legroom for the low voltage supply picked in the middle.
But the circuitry suffices many needs. I use a similar supply for a small tube amplifier:
http://www.mcamafia.de/tubes/soc/soc_en.htm
(which is a link within http://www.mcamafia.de/tubes/keksdose/cookiebox.htm)
It does not work *that* well, since the transformers I picked are a tad too small, but it shows the principle quite well.
Jan 07, 2009
How about something like this:
Figure 1. 12/230 VDC power supply circuit
(Circuit Courtesy of Peter Wendt)
Or this (looks like pulse output, but probably doesn't matter that much):
Figure 2. Variable HV DC power supply circuit
(Version 1.93, Copyright © 1994-2005, Samuel M. Goldwasser, All Rights Reserved, For contact info, please see the Sci.Electronics.Repair FAQ Email Links Page. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying.)
Can anyone get a hold of this paper:
Analytical Biochemistry, Volume 137, Issue 1, 15 February 1984, Pages 156-160, An economic “power supply” using a diode for agarose and polyacrylamide gel electrophoresis, Y. Kadokami, K. Takao and K. Saigo
- This is an interesting paper; *jcline@ieee.org 18:40, 8 January 2009 (EST):
- They show that a simple unregulated half-wave supply works fine for running gels. This means ripple is not an issue. I guess the gel acts as a big capacitor. The resulting DC voltage across the gel would be Vrms = Vpk / sqrt(2). Where, Vpk = (1/2) Vpk-pk. i.e. if AC input voltage is 120V, then Vrms = 60 * 0.707. (For some reason they state that at AC input voltage of 100V, that the resultant output would be "about 50V" which is not correct. Also, the "power company supplies 100V" is not correct either -- do not trust the wall outlet to ever be more than 15% accurate.)
- "1 to 2.5 V/cm" is found to work best for gels. Need to check the Gel Box 2.0 physical measurements to calculate total voltage for the P/S.
- This is an interesting paper; *jcline@ieee.org 18:40, 8 January 2009 (EST):
Jan 06, 2009
Is there any way to move the power supply discussion from the diybio mailing list to this page? Should we? We could make diybio post inviting the interested parties to come here, and sign in (like on a contributors page -- is there a way to add more pages?). I'd like to see us have a meeting, get organized, and make some progress. Phil...
Prior Mailing list discussions
- Jonathan Cline, Wed, 07 Jan 2009 00:13:08 -0600
Yes, I think this approach is the best way to go: use an off the shelf switching supply as the master supply (probably a computer supply - very ubiquitous), then add step up circuit(s). Choosing whether LM317 is appropriate or not is premature, before design criteria are established. These questions are important: - what is the maximum noise allowed in the voltage? (someone mentioned voltage fluctuations are not important; this could be a factor since different designs might trade off "perfectly flat DC" for some ripple in the output) - what is the maximum noise allowed in the current? - is the voltage limted to a range? Yes ; 20v-600v - is the current limited to a range? <- this is the important one - what is the total power dissipation? Answer all these before proceeding further with the design. Other interesting questions might be.. what is the slew rate requirement (how fast does the voltage need to go from 0v to maximum, once it is switched on, and how fast does it need to go back to 0v, when switched off); likely this is "slow is ok". What is the resolution of the voltage steps, i.e. does the setting need to be +/- 1v, or +/- 10v, or +/- 100v? Web surfing today, I saw some comments on a blog (presumably from a bio lab guy) that "I always run my gels current limited to 100mA in the lab". It seems different people set different current limits; other guys said they were setting 250mA, or 300mA, or 400mA. P total = V * I to calculate maximum power needed for the master supply (add 30% to 50% for overheat loss; which is mostly heat). If 100mA and 600v, then it's ~60W. If 100mA and 100v, then it's ~10W. At the range of <20W, then a much smaller supply could be used as the master. For example, optimal might be a laptop supply brick, which are very common, and price -vs- value makes it very cheap; you won't be able to build a good master supply for what they now manufacture in china & sell computer or laptop supplies at discount.. If current limiting is a factor in electrophoresis, then you will want a constant current circuit as well as voltage doubler after the master supply. I dont think the PDF you quoted is applicable, once you answer the "how much current" question; it seemed applicable for small milliamp range only (" the maximum output current reaches 1 mA"). Define the Specs first, then design second. Why is variable voltage even needed? If "DIY, Inc." controls the entire process (gel box + power supply + agar kit + buffer kit) then the voltage should not need to be varied, and can be fixed. There are times when it is suitable to force a standard into place, just by picking one, and not allowing choice. Standardizing the process may be one way to simplify the protocols, remove "choice" from the user's feature list, and simplify the design too. Just an idea - I don't know if this is applicable in this case. Variable voltage might be needed in labs to optimize protocols, or as a multi-use supply, or maybe "because I like 245 volts and I've always used that voltage anyway, and I ain't changing it". If the entire process is already optimized by the manufacturer (i.e. Jason), then why need to change the voltage? Thus, the p/s is part of the gel box 'system design'. Everything can be optimized to work together. The drawback is that the components may not be interchangeable with other boxes or protocols. This drawback may be a good tradeoff.
- JonathanCline, Tues, Jan 6 2009 8:56 am
On Jan 5, 10:11 pm, "Meredith L. Patterson" <clonea...@gmail.com> wrote: > > On Mon, Jan 5, 2009 at 7:26 PM, Jason Morrison > > > > <jason.p.morri...@gmail.com> wrote: >> > > A timer also seems to be a good feature. > > > > I'd just use a microcontroller for that. Prototype it on an arduino, > > use pushbutton switches or a potentiometer to set the time (you can > > even use a couple of 7-segment LEDs, or a $10 LCD, to display the time > > and a countdown). I've already prototyped something nearly identical, > > also on an arduino, for the DIY electroporator; for the final version > > it'll be a $3 Atmel AVR. Add a piezo speaker to make it beep when it's > > done or whatever. Although microcontrollers might be cheap nowadays, using a microcontroller should always be avoided if possible, using analog or discrete electronics (non-software parts) instead. The microcontroller adds a lot of complexity to the circuit and a lot of opportunity for software bugs. Especially in a power circuit. A simpler to build, more foolproof to error, timer circuit is to use a 555 timer chip in one-shot mode. Example circuits are widespread. Use 556 for two timers in one chip. The time can be modified with a potentiometer (volume knob). The resolution and repetition is set with fixed components (resistors + capacitors). The design criteria are: - the timer doesn't need high resolution - the maximum time can be fixed in the circuit, and time control can vary linearly in that range - the timer can be automatically set by the power supply voltage (click the "600v" setting and the timer is set to X mins; click the "100v" setting and the timer is set to Y mins) - the potentiometer can be calibrated so that the scale marking reads approximate times (i.e. "45 mins" might mean 45 mins ± 1 minute) The "Faster Better Media" also mentions that running a gel with a stepped voltage supply can decrease total time. i.e. run at 500V for X mins, then run at 50v for Y mins. This could be done with a dual timer circuit. > > The fancy-schmancy (but broken) Bio-Rad electrophoresis power supply I > > have does two outputs, and each can be programmed separately to run a > > timed sequence. This sort of logic is not difficult to program and I > > really don't get why the supply costs thousands of dollars. The > > green-and-white box is pretty, but not that pretty. What is the total power requirement for running gels. Some of the commercial supplies are listed as 25W or 50W. It would be a bad idea to "hook the gel up to the wall outlet" as someone mentions later. Bad, bad, bad. The user might end up researching the life-after-death experience. The main purpose of a regulated supply is to regulate voltage and current: limit voltage for proper operation of the circuit and limit current to limit safety issues. Internationalization is also important. A supply which plugs into AC120V/60Hz for north america is worthless in europe and much of asia, since those countries are AC200V/50Hz. It might be a better design to use a common international switching supply (a small 60W computer power supply) and add a voltage multiplier to step up the voltage to the desired gel voltage; this allows the wall-side to plug into international power. The power supply could also be physically tied to the gel itself for thermal regulation. In the "Faster Better Media" references, it mentions that running high voltage gels for fast operation has the drawback of excessive heat dissipation, and too much heat can ruin the experiment. The power supply can be thermally regulated by mechanically coupling the gel box to the power supply regulator (that means, bolt a block of metal to both the gel box and the regulator chip). Because the regulator chip has a built-in thermal shutoff (some of these are programmable as well, by voltage input), the power supply can be made to decrease in voltage as temperature rises, or stop supplying after a voltage threshold. This is a discrete circuit design, not microcontroller based (which is better, because it won't have software bugs). ## Jonathan Cline