Many Paccomm Tiny-2 Mk2 TNCs have a polarised capacitor installed incorrectly. They become leaky and it degrades performance.
Let’s look at the datasheet for a MAX231 and review the charge pump and related filter capacitors.
Note especially the capacitor connected from pin 3 to ground, it is an electrolytic with -ve terminal to pin 3 and it develops the -ve voltage for the true RS-232 line driver. Continue reading Paccomm Tiny-2 Mk2 capacitor polarity problem
This article presents a derivation of the expression for the unknown impedance in an s21 series through measurement.
Recall that S parameters are with respect to some reference impedance Zref, commonly 50+jΩ, but not necessarily. This article and the references assume Zref=50+jΩ.
The diagram above is from (Agilent 2009) and illustrates the configuration of a series-through impedance measurement. Continue reading Derivation of the expression for the unknown impedance in an s21 series through measurement
The deck is a fabricated deck on a Toro MX 4250 residential zero turn mower, it has 200h of service over 8 years… which is not very much.
The deck has the recycler option installed.
Deck service included:
Jiggling the blade tips showed 2-3mm vertical play in both spindles. New bearings have much less play, undetectable without instruments.
The spindles are easily serviced.
The lower bearing is one spindle had a rusted retainer / separator and collapsed when driving it from the housing. The other lower bearing was rough, but did not collapse. The top bearings were in good condition.
A set of four NSK 6203-2RS bearings was purchased ($35) to replace all the bearings.
Both idler pulleys were dry of grease. It was possible to pop the rubber seal and pack a little more grease pending arrival of replacement parts.
Replacement parts were purchased for $60 (inc shipping) and fitted.
The message is that water sprayed over the top of the deck assembly is retained in a shallow cup on the sealed bearings and some will wind up inside the bearings… don’t wash the top of the deck.
Above, the underside of the deck after washing, de-scaling with a pneumatic needle scaler, power brushing with a cup brush, and another high pressure wash ready for application of corrosion protection. Continue reading Mower deck maintenance – Toro MX 4250
It is now near impossible to procure a genuine STLINKV2 or a good clone. Newer versions of STM32CubeProgrammer will not work with poor clones.
In pursuit of a small inexpensive replacement for the STLINKV2, the STLINKV3-MINIE is a candidate. That said, they can be difficult to source… mine is on 9 months wait from element14.
Above is the STLINKV3-MINIE (~$20). Continue reading A low cost break-out board for STDC14
A correspondent asked how to program a PIC 12F510 used in one of my projects using his DIY-150 programmer.
The DIY-150 programmer is quite an old design and there has been no development for more than 10 years, meaning no new chips added, though there are lots of online sellers of the now stale design.
The 12F510 is very similar to the 12F509 which microbrn v150807 does support. The 12F510 can be programmed by selecting chip type 12F509.
Alternatively, download the archive below and extract a modified chipdata.cid file which includes a 12F510, and extract it to replace the existing installed file.
The revised chipdata.cid can be downloaded here: chipdata.7z.
This article documents capture of starter motor current on a Toro MX4250 mower with the Toro V-twin engine. The test is part of diagnosis of possible starter motor problems.
The current was captured with a Owon HDS242S hand held DSO and Hantek CC-650 current probe.
The motor is a permanent magnet DC motor with bendix gear.
Above is a screenshot, vertical scale is 50A/div, measurement is of battery current. Continue reading Review of mower starter motor current using Owon HDS242S and Hantek CC-650